right side of assignment cannot be destructured safari

Typeerror: right side of assignment cannot be destructured

The error message “TypeError: right side of assignment cannot be destructured” occurs when you try to destructure an invalid or non-destructurable value on the right side of an assignment.

To understand this error, let’s first explain what destructuring assignment is. Destructuring assignment is a feature in JavaScript that allows you to extract values from arrays or objects and assign them to variables in a concise and readable way.

Here’s an example of correct usage of destructuring assignment:

In the above example, the array is destructured and its values are assigned to variables a, b, and c respectively. This is a valid usage and will work as expected.

Now, let’s see an example that can cause the “TypeError: right side of assignment cannot be destructured” error:

In the above example, we are trying to destructure the value variable, which is not an array or an object. This is an invalid usage of destructuring assignment, and it will result in the mentioned error.

To fix this error, ensure that the right side of the assignment is a valid destructurable value, such as an array or an object. If you want to destructure a value that is not an array or an object, you can wrap it in an array or object literal to make it valid.

In the above fixed example, we wrapped the value variable in an array literal, allowing us to destructure it without causing an error. However, note that since the wrapped value is not an array with three elements, variables y and z are assigned with the value “undefined”.

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Destructuring assignment

The destructuring assignment syntax is a JavaScript expression that makes it possible to unpack values from arrays, or properties from objects, into distinct variables.

Description

The object and array literal expressions provide an easy way to create ad hoc packages of data.

The destructuring assignment uses similar syntax but uses it on the left-hand side of the assignment instead. It defines which values to unpack from the sourced variable.

Similarly, you can destructure objects on the left-hand side of the assignment.

This capability is similar to features present in languages such as Perl and Python.

For features specific to array or object destructuring, refer to the individual examples below.

Binding and assignment

For both object and array destructuring, there are two kinds of destructuring patterns: binding pattern and assignment pattern , with slightly different syntaxes.

In binding patterns, the pattern starts with a declaration keyword ( var , let , or const ). Then, each individual property must either be bound to a variable or further destructured.

All variables share the same declaration, so if you want some variables to be re-assignable but others to be read-only, you may have to destructure twice — once with let , once with const .

In many other syntaxes where the language binds a variable for you, you can use a binding destructuring pattern. These include:

• The looping variable of for...in for...of , and for await...of loops;
• Function parameters;
• The catch binding variable.

In assignment patterns, the pattern does not start with a keyword. Each destructured property is assigned to a target of assignment — which may either be declared beforehand with var or let , or is a property of another object — in general, anything that can appear on the left-hand side of an assignment expression.

Note: The parentheses ( ... ) around the assignment statement are required when using object literal destructuring assignment without a declaration.

{ a, b } = { a: 1, b: 2 } is not valid stand-alone syntax, as the { a, b } on the left-hand side is considered a block and not an object literal according to the rules of expression statements . However, ({ a, b } = { a: 1, b: 2 }) is valid, as is const { a, b } = { a: 1, b: 2 } .

If your coding style does not include trailing semicolons, the ( ... ) expression needs to be preceded by a semicolon, or it may be used to execute a function on the previous line.

Note that the equivalent binding pattern of the code above is not valid syntax:

You can only use assignment patterns as the left-hand side of the assignment operator. You cannot use them with compound assignment operators such as += or *= .

Default value

Each destructured property can have a default value . The default value is used when the property is not present, or has value undefined . It is not used if the property has value null .

The default value can be any expression. It will only be evaluated when necessary.

Rest property

You can end a destructuring pattern with a rest property ...rest . This pattern will store all remaining properties of the object or array into a new object or array.

The rest property must be the last in the pattern, and must not have a trailing comma.

Array destructuring

Basic variable assignment, destructuring with more elements than the source.

In an array destructuring from an array of length N specified on the right-hand side of the assignment, if the number of variables specified on the left-hand side of the assignment is greater than N , only the first N variables are assigned values. The values of the remaining variables will be undefined.

Swapping variables

Two variables values can be swapped in one destructuring expression.

Without destructuring assignment, swapping two values requires a temporary variable (or, in some low-level languages, the XOR-swap trick ).

Parsing an array returned from a function

It's always been possible to return an array from a function. Destructuring can make working with an array return value more concise.

In this example, f() returns the values [1, 2] as its output, which can be parsed in a single line with destructuring.

Ignoring some returned values

You can ignore return values that you're not interested in:

You can also ignore all returned values:

Using a binding pattern as the rest property

The rest property of array destructuring assignment can be another array or object binding pattern. The inner destructuring destructures from the array created after collecting the rest elements, so you cannot access any properties present on the original iterable in this way.

These binding patterns can even be nested, as long as each rest property is the last in the list.

On the other hand, object destructuring can only have an identifier as the rest property.

Unpacking values from a regular expression match

When the regular expression exec() method finds a match, it returns an array containing first the entire matched portion of the string and then the portions of the string that matched each parenthesized group in the regular expression. Destructuring assignment allows you to unpack the parts out of this array easily, ignoring the full match if it is not needed.

Using array destructuring on any iterable

Array destructuring calls the iterable protocol of the right-hand side. Therefore, any iterable, not necessarily arrays, can be destructured.

Non-iterables cannot be destructured as arrays.

Iterables are only iterated until all bindings are assigned.

The rest binding is eagerly evaluated and creates a new array, instead of using the old iterable.

Object destructuring

Basic assignment, assigning to new variable names.

A property can be unpacked from an object and assigned to a variable with a different name than the object property.

Here, for example, const { p: foo } = o takes from the object o the property named p and assigns it to a local variable named foo .

Assigning to new variable names and providing default values

A property can be both

• Unpacked from an object and assigned to a variable with a different name.
• Assigned a default value in case the unpacked value is undefined .

Unpacking properties from objects passed as a function parameter

Objects passed into function parameters can also be unpacked into variables, which may then be accessed within the function body. As for object assignment, the destructuring syntax allows for the new variable to have the same name or a different name than the original property, and to assign default values for the case when the original object does not define the property.

Consider this object, which contains information about a user.

Here we show how to unpack a property of the passed object into a variable with the same name. The parameter value { id } indicates that the id property of the object passed to the function should be unpacked into a variable with the same name, which can then be used within the function.

You can define the name of the unpacked variable. Here we unpack the property named displayName , and rename it to dname for use within the function body.

Nested objects can also be unpacked. The example below shows the property fullname.firstName being unpacked into a variable called name .

Setting a function parameter's default value

Default values can be specified using = , and will be used as variable values if a specified property does not exist in the passed object.

Below we show a function where the default size is 'big' , default co-ordinates are x: 0, y: 0 and default radius is 25.

In the function signature for drawChart above, the destructured left-hand side has a default value of an empty object = {} .

You could have also written the function without that default. However, if you leave out that default value, the function will look for at least one argument to be supplied when invoked, whereas in its current form, you can call drawChart() without supplying any parameters. Otherwise, you need to at least supply an empty object literal.

For more information, see Default parameters > Destructured parameter with default value assignment .

Nested object and array destructuring

For of iteration and destructuring, computed object property names and destructuring.

Computed property names, like on object literals , can be used with destructuring.

Invalid JavaScript identifier as a property name

Destructuring can be used with property names that are not valid JavaScript identifiers by providing an alternative identifier that is valid.

Destructuring primitive values

Object destructuring is almost equivalent to property accessing . This means if you try to destruct a primitive value, the value will get wrapped into the corresponding wrapper object and the property is accessed on the wrapper object.

Same as accessing properties, destructuring null or undefined throws a TypeError .

This happens even when the pattern is empty.

Combined array and object destructuring

Array and object destructuring can be combined. Say you want the third element in the array props below, and then you want the name property in the object, you can do the following:

The prototype chain is looked up when the object is deconstructed

When deconstructing an object, if a property is not accessed in itself, it will continue to look up along the prototype chain.

Specifications

Browser compatibility.

BCD tables only load in the browser with JavaScript enabled. Enable JavaScript to view data.

• Assignment operators
• ES6 in Depth: Destructuring on hacks.mozilla.org (2015)

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WordPress 6.2 and Safari 13.1.2

2023 03 31 I have just updated our WordPress to 6.2. Now, Safari does not load the “edit” page. The page is blank. I can open the dashboard, and select a page to edit, but the page does not open. I am using MacOS 13.6.1.

Here are the Errors I get trying to edit the WordPress page after updating to version WP6.2 in Safari 13.1.2

[Error] SyntaxError: Unexpected token ‘;’. Expected an opening ‘(‘ before a method’s parameter list. (anonymous function) (block-editor.min.js:26) [Error] TypeError: a.addEventListener is not a function. (In ‘a.addEventListener(“change”,r)’, ‘a.addEventListener’ is undefined) (anonymous function) (viewport.min.js:2:1382) map flatIntoArrayWithCallback d (viewport.min.js:2:1267) (anonymous function) (viewport.min.js:2:2173) Global Code (viewport.min.js:2:2311) [Error] TypeError: undefined is not an object (evaluating ‘Qe.withColors’) (anonymous function) (block-library.min.js:14:17374) (anonymous function) (block-library.min.js:14:620310) Global Code (block-library.min.js:14:620354) [Error] TypeError: undefined is not an object (evaluating ‘p.SETTINGS_DEFAULTS’) (anonymous function) (editor.min.js:19:21334) (anonymous function) (editor.min.js:19:147355) Global Code (editor.min.js:19:147393) [Error] TypeError: undefined is not an object (evaluating ‘G.ifViewportMatches’) (anonymous function) (edit-post.min.js:7:52490) (anonymous function) (edit-post.min.js:7:125591) Global Code (edit-post.min.js:7:125631) [Error] TypeError: Right side of assignment cannot be destructured (anonymous function) (classic-paragraph.js:1:1053) o (classic-paragraph.js:1:115) (anonymous function) (classic-paragraph.js:1:904) Global Code (classic-paragraph.js:1:912) [Error] TypeError: Right side of assignment cannot be destructured (anonymous function) (richtext-buttons.js:1:1028) o (richtext-buttons.js:1:115) (anonymous function) (richtext-buttons.js:1:904) Global Code (richtext-buttons.js:1:912) [Error] TypeError: undefined is not an object (evaluating ‘wp.blockEditor.InspectorControls’) (anonymous function) (blocks.build.js:1:1611) t (blocks.build.js:1:106) (anonymous function) (blocks.build.js:1:542) t (blocks.build.js:1:106) (anonymous function) (blocks.build.js:1:453) Global Code (blocks.build.js:1:461) [Error] TypeError: undefined is not an object (evaluating ‘wp.editPost.initializeEditor’) (anonymous function) (post.php:280)

You’ve posted to the free support forums for websites hosted here at WordPress.com. Since your site is not hosted with us, we’re limited in what we can help with and advise. But I can get you pointed in the right direction to get help.

If you’re having an issue after upgrading to WordPress 6.2, you should check this post over on WordPress.org first: https://wordpress.org/support/topic/read-this-first-wordpress-6-2/

If you still have trouble, please reach out to the WordPress community for guidance:

https://wordpress.org/support/forum/how-to-and-troubleshooting

I hope that clarifies things!

• The topic ‘WordPress 6.2 and Safari 13.1.2’ is closed to new replies.

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Destructuring and parameter handling in ECMAScript 6

ECMAScript 6 (ES6) supports destructuring , a convenient way to extract values from data stored in (possibly nested) objects and arrays. This blog post describes how it works and gives examples of its usefulness. Additionally, parameter handling receives a significant upgrade in ES6: it becomes similar to and supports destructuring, which is why it is explained here, too.

Destructuring   #

In locations that receive data (such as the left-hand side of an assignment), destructuring lets you use patterns to extract parts of that data. In the following example, we use destructuring in a variable declaration (line (A)). It declares the variables f and l and assigns them the values 'Jane' and 'Doe' .

Destructuring can be used in the following locations. Each time, x is set to 'a' .

Constructing versus extracting   #

To fully understand what destructuring is, let’s first examine its broader context. JavaScript has operations for constructing data:

And it has operations for extracting data:

Note that we are using the same syntax that we have used for constructing.

There is nicer syntax for constructing – an object literal :

Destructuring in ECMAScript 6 enables the same syntax for extracting data, where it is called an object pattern :

Just as the object literal lets us create multiple properties at the same time, the object pattern lets us extract multiple properties at the same time.

You can also destructure arrays via patterns:

We distinguish:

• Destructuring source: the data to be destructured. For example, the right-hand side of a destructuring assignment.
• Destructuring target: the pattern used for destructuring. For example, the left-hand side of a destructuring assignment.

Being selective with parts   #

If you destructure an object, you are free to mention only those properties that you are interested in:

If you destructure an array, you can choose to only extract a prefix:

If a part has no match   #

Similarly to how JavaScript handles non-existent properties and array elements, destructuring silently fails if the target mentions a part that doesn’t exist in the source: the interior of the part is matched against undefined . If the interior is a variable that means that the variable is set to undefined :

Nesting   #

You can nest patterns arbitrarily deeply:

How do patterns access the innards of values?   #

In an assignment pattern = someValue , how does the pattern acess what’s inside someValue ?

Object patterns coerce values to objects   #

The object pattern coerces destructuring sources to objects before accessing properties. That means that it works with primitive values:

Failing to object-destructure a value   #

The coercion to object is not performed via Object() , but via the internal operation ToObject() . Object() never fails:

ToObject() throws a TypeError if it encounters undefined or null . Therefore, the following destructurings fail, even before destructuring accesses any properties:

As a consequence, you can use the empty object pattern {} to check whether a value is coercible to an object. As we have seen, only undefined and null aren’t:

The parentheses around the object patterns are necessary because statements must not begin with curly braces in JavaScript.

Array patterns work with iterables   #

Array destructuring uses an iterator to get to the elements of a source. Therefore, you can array-destructure any value that is iterable. Let’s look at examples of iterable values.

Strings are iterable:

Don’t forget that the iterator over strings returns code points (“Unicode characters”, 21 bits), not code units (“JavaScript characters”, 16 bits). (For more information on Unicode, consult the chapter “ Chapter 24. Unicode and JavaScript ” in “Speaking JavaScript”.) For example:

You can’t access the elements of a set [1] via indices, but you can do so via an iterator. Therefore, array destructuring works for sets:

The Set iterator always returns elements in the order in which they were inserted, which is why the result of the previous destructuring is always the same.

Infinite sequences. Destructuring also works for iterators over infinite sequences. The generator function allNaturalNumbers() returns an iterator that yields 0, 1, 2, etc.

The following destructuring extracts the first three elements of that infinite sequence.

Failing to array-destructure a value   #

A value is iterable if it has a method whose key is Symbol.iterator that returns an object. Array-destructuring throws a TypeError if the value to be destructured isn’t iterable:

The TypeError is thrown even before accessing elements of the iterable, which means that you can use the empty array pattern [] to check whether a value is iterable:

Default values   #

Default values are a feature of patterns:

• Each part of a pattern can optionally specify a default value.
• If the part has no match in the source, destructuring continues with the default value (if one exists) or undefined .

Let’s look at an example. In the following destructuring, the element at index 0 has no match on the right-hand side. Therefore, destructuring continues by matching x against 3, which leads to x being set to 3.

You can also use default values in object patterns:

Default values are also used if a part does have a match and that match is undefined :

The rationale for this behavior is explained later, in the section on parameter default values.

Default values are computed on demand   #

The default values themselves are only computed when they are needed. That is, this destructuring:

is equivalent to:

You can observe that if you use console.log() :

In the second destructuring, the default value is not needed and log() is not called.

Default values can refer to other variables in the pattern   #

A default value can refer to any variable, including another variable in the same pattern:

However, order matters: the variables x and y are declared from left to right and produce a ReferenceError if they are accessed before their declaration.

Default values for patterns   #

So far we have only seen default values for variables, but you can also associate them with patterns:

What does this mean? Recall the rule for default values:

If the part has no match in the source, destructuring continues with the default value […].

The element at index 0 has no match, which is why destructuring continues with:

You can more easily see why things work this way if you replace the pattern { prop: x } with the variable pattern :

More complex default values. Let’s further explore default values for patterns. In the following example, we assign a value to x via the default value { prop: 123 } :

Because the array element at index 0 has no match on the right-hand side, destructuring continues as follows and x is set to 123.

However, x is not assigned a value in this manner if the right-hand side has an element at index 0, because then the default value isn’t triggered.

In this case, destructuring continues with:

Thus, if you want x to be 123 if either the object or the property is missing, you need to specify a default value for x itself:

Here, destructuring continues as follows, independently of whether the right-hand side is [{}] or [] .

More object destructuring features   #

Property value shorthands   #.

Property value shorthands [2] are a feature of object literals: If the value of a property is provided via a variable whose name is the same as the key, you can omit the key. This works for destructuring, too:

This declaration is equivalent to:

You can also combine property value shorthands with default values:

Computed property keys   #

Computed property keys [2:1] are another object literal feature that also works for destructuring: You can specify the key of a property via an expression, if you put it in square brackets:

Computed property keys allow you to destructure properties whose keys are symbols [3] :

More array destructuring features   #

Elision   #.

Elision lets you use the syntax of array “holes” to skip elements during destructuring:

Rest operator   #

The rest operator ( ... ) lets you extract the remaining elements of an array into an array. You can only use the operator as the last part inside an array pattern:

[Note: This operator extracts data. The same syntax ( ... ) is used by the spread operator , which constructs and is explained later.]

If the operator can’t find any elements, it matches its operand against the empty array. That is, it never produces undefined or null . For example:

The operand of the rest operator doesn’t have to be a variable, you can use patterns, too:

The rest operator triggers the following destructuring:

You can assign to more than just variables   #

If you assign via destructuring, each variable part can be everything that is allowed on the left-hand side of a normal assignment, including a reference to a property ( obj.prop ) and a reference to an array element ( arr[0] ).

You can also assign to object properties and array elements via the rest operator ( ... ):

If you declare variables via destructuring then you must use simple identifiers, you can’t refer to object properties and array elements.

Pitfalls of destructuring   #

There are two things to be mindful of when using destructuring.

Don’t start a statement with a curly brace   #

Because code blocks begin with a curly brace, statements must not begin with one. This is unfortunate when using object destructuring in an assignment:

The work-around is to either put the pattern in parentheses or the complete expression:

You can’t mix declaring and assigning to existing variables   #

Within a destructuring variable declaration, every variable in the source is declared. In the following example, we are trying to declare the variable b and refer to the existing variable f , which doesn’t work.

The fix is to use a destructuring assignment and to declare b beforehand:

Examples of destructuring   #

Let’s start with a few smaller examples.

The for-of loop [4] supports destructuring:

You can use destructuring to swap values. That is something that engines could optimize, so that no array would be created.

You can use destructuring to split an array:

Destructuring return values   #

Some built-in JavaScript operations return arrays. Destructuring helps with processing them:

exec() returns null if the regular expression doesn’t match. Unfortunately, you can’t handle null via default values, which is why you must use the Or operator ( || ) in this case:

Multiple return values   #

To see the usefulness of multiple return values, let’s implement a function findElement(a, p) that searches for the first element in the array a for which the function p returns true . The question is: what should that function return? Sometimes one is interested in the element itself, sometimes in its index, sometimes in both. The following implementation does both.

In line (A), the array method entries() returns an iterable over [index,element] pairs. We destructure one pair per iteration. In line (B), we use property value shorthands to return the object { element: element, index: index } .

In the following example, we use several ECMAScript features to write more concise code: An arrow functions helps us with defining the callback, destructuring and property value shorthands help us with handling the return value.

Due to index and element also referring to property keys, the order in which we mention them doesn’t matter:

We have successfully handled the case of needing both index and element. What if we are only interested in one of them? It turns out that, thanks to ECMAScript 6, our implementation can take care of that, too. And the syntactic overhead compared to functions that support only elements or only indices is minimal.

Each time, we only extract the value of the one property that we need.

Parameter handling   #

Parameter handling has been significantly upgraded in ECMAScript 6. It now supports parameter default values, rest parameters (varags) and destructuring. The new way of handling parameters is equivalent to destructuring the actual parameters via the formal parameters. That is, the following function call:

Let’s look at specific features next.

Parameter default values   #

ECMAScript 6 lets you specify default values for parameters:

Omitting the second parameter triggers the default value:

Watch out – undefined triggers the default value, too:

The default value is computed on demand, only when it is actually needed:

Why does undefined trigger default values?   #

It isn’t immediately obvious why undefined should be interpreted as a missing parameter or a missing part of an object or array. The rationale for doing so is that it enables you to delegate the definition of default values. Let’s look at two examples.

In the first example (source: Rick Waldron’s TC39 meeting notes from 2012-07-24 ), we don’t have to define a default value in setOptions() , we can delegate that task to setLevel() .

In the second example, square() doesn’t have to define a default for x , it can delegate that task to multiply() :

Default values further entrench the role of undefined as indicating that something doesn’t exist, versus null indicating emptiness.

Referring to other variables in default values   #

Within a parameter default value, you can refer to any variable, including other parameters:

However, order matters: parameters are declared from left to right and within a default value, you get a ReferenceError if you access a parameter that hasn’t been declared, yet.

Default values exist in their own scope, which is between the “outer” scope surrounding the function and the “inner” scope of the function body. Therefore, you can’t access inner variables from the default values:

If there were no outer x in the previous example, the default value x would produce a ReferenceError .

Rest parameters   #

Putting the rest operator ( ... ) in front of the last formal parameter means that it will receive all remaining actual parameters in an array.

If there are no remaining parameters, the rest parameter will be set to the empty array:

No more arguments !   #

Rest parameters can completely replace JavaScript’s infamous special variable arguments . They have the advantage of always being arrays:

One interesting feature of arguments is that you can have normal parameters and an array of all parameters at the same time:

You can avoid arguments in such cases if you combine a rest parameter with array destructuring. The resulting code is longer, but more explicit:

Note that arguments is iterable [4:1] in ECMAScript 6, which means that you can use for-of and the spread operator:

Simulating named parameters   #

When calling a function (or method) in a programming language, you must map the actual parameters (specified by the caller) to the formal parameters (of a function definition). There are two common ways to do so:

Positional parameters are mapped by position. The first actual parameter is mapped to the first formal parameter, the second actual to the second formal, and so on.

Named parameters use names (labels) to perform the mapping. Names are associated with formal parameters in a function definition and label actual parameters in a function call. It does not matter in which order named parameters appear, as long as they are correctly labeled.

Named parameters have two main benefits: they provide descriptions for arguments in function calls and they work well for optional parameters. I’ll first explain the benefits and then show you how to simulate named parameters in JavaScript via object literals.

Named Parameters as Descriptions   #

As soon as a function has more than one parameter, you might get confused about what each parameter is used for. For example, let’s say you have a function, selectEntries() , that returns entries from a database. Given the function call:

what do these two numbers mean? Python supports named parameters, and they make it easy to figure out what is going on:

Optional Named Parameters   #

Optional positional parameters work well only if they are omitted at the end. Anywhere else, you have to insert placeholders such as null so that the remaining parameters have correct positions.

With optional named parameters, that is not an issue. You can easily omit any of them. Here are some examples:

Simulating Named Parameters in JavaScript   #

JavaScript does not have native support for named parameters like Python and many other languages. But there is a reasonably elegant simulation: name parameters via an object literal, passed as a single actual parameter. When you use this technique, an invocation of selectEntries() looks like:

The function receives an object with the properties start , end , and step . You can omit any of them:

In ECMAScript 5, you’d implement selectEntries() as follows:

In ECMAScript 6, you can use destructuring, which looks like this:

If you call selectEntries() with zero arguments, the destructuring fails, because you can’t match an object pattern against undefined . That can be fixed via a default value. In the following code, the object pattern is matched against {} if there isn’t at least one argument.

You can also combine positional parameters with named parameters. It is customary for the latter to come last:

In principle, JavaScript engines could optimize this pattern so that no intermediate object is created, because both the object literals at the call sites and the object patterns in the function definitions are static.

Note: In JavaScript, the pattern for named parameters shown here is sometimes called options or option object (e.g., by the jQuery documentation).

Pitfall: destructuring a single arrow function parameter   #

Arrow functions have a special single-parameter version where no parentheses are needed:

The single-parameter version does not support destructuring:

Examples of parameter handling   #

Foreach() and destructuring   #.

You will probably mostly use the for-of loop in ECMAScript 6, but the array method forEach() also profits from destructuring. Or rather, its callback does.

First example: destructuring the arrays in an array.

Second example: destructuring the objects in an array.

Transforming maps   #

An ECMAScript 6 Map [1:1] doesn’t have a method map() (like arrays). Therefore, one has to:

• Convert it to an array of [key,value] pairs.
• map() the array.
• Convert the result back to a map.

This looks as follows.

Handling an array returned via a Promise   #

The tool method Promise.all() [5] works as follows:

• Input: an array of Promises.
• Output: a Promise that resolves to an array as soon as the last input Promise is resolved. The array contains the resolutions of the input Promises.

Destructuring helps with handling the array that the result of Promise.all() resolves to:

fetch() is a Promise-based version of XMLHttpRequest . It is part of the Fetch standard .

Required parameters   #

In ECMAScript 5, you have a few options for ensuring that a required parameter has been provided, which are all quite clumsy:

In ECMAScript 6, you can (ab)use default parameter values to achieve more concise code (credit: idea by Allen Wirfs-Brock):

Interaction:

Enforcing a maximum arity   #

This section presents three approaches to enforcing a maximum arity. The running example is a function f whose maximum arity is 2 – if a caller provides more than 2 parameters, an error should be thrown.

The first approach collects all actual parameters in the formal rest parameter args and checks its length.

The second approach relies on unwanted actual parameters appearing in the formal rest parameter extra .

The third approach uses a sentinel value that is gone if there is a third parameter. One caveat is that the default value OK is also triggered if there is a third parameter whose value is undefined .

Sadly, each one of these approaches introduces significant visual and conceptual clutter. I’m tempted to recommend checking arguments.length , but I also want arguments to go away.

The spread operator ( ... )   #

The spread operator ( ... ) is the opposite of the rest operator: Where the rest operator extracts arrays, the spread operator turns the elements of an array into the arguments of a function call or into elements of another array.

Spreading into function and method calls   #

Math.max() is a good example for demonstrating how the spread operator works in method calls. Math.max(x1, x2, ···) returns the argument whose value is greatest. It accepts an arbitrary number of arguments, but can’t be applied to arrays. The spread operator fixes that:

In contrast to the rest operator, you can use the spread operator anywhere in a sequence of parts:

Another example is JavaScript not having a way to destructively append the elements of one array to another one. However, arrays do have the method push(x1, x2, ···) , which appends all of its arguments to its receiver. The following code shows how you can use push() to append the elements of arr2 to arr1 .

Spreading into constructors   #

In addition to function and method calls, the spread operator also works for constructor calls:

That is something that is difficult to achieve in ECMAScript 5 .

Spreading into arrays   #

The spread operator can also be used inside arrays:

That gives you a convenient way to concatenate arrays:

Converting iterable or array-like objects to arrays   #

The spread operator lets you convert any iterable object to an array:

Let’s convert a set [1:2] to an array:

Your own iterable objects [4:2] can be converted to arrays in the same manner:

Note that, just like the for-of loop, the spread operator only works for iterable objects. Most important objects are iterable: arrays, maps, sets and arguments . Most DOM data structures will also eventually be iterable.

Should you ever encounter something that is not iterable, but array-like (indexed elements plus a property length ), you can use Array.from() [6] to convert it to an array:

Further reading:   #

ECMAScript 6: maps and sets ↩︎ ↩︎ ↩︎

ECMAScript 6: new OOP features besides classes ↩︎ ↩︎

Symbols in ECMAScript 6 ↩︎

Iterators and generators in ECMAScript 6 ↩︎ ↩︎ ↩︎

ECMAScript 6 promises (2/2): the API ↩︎

ECMAScript 6’s new array methods ↩︎

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Cannot destruct right side of assignment

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Resolved   TypeError data.site is null

• Thread starter rik
• Start date Dec 4, 2023

Basic Pleskian

• Dec 4, 2023

Even if you check with plesk repair all -n, everything will be OK. I checked with plesk repair all -n and everything is OK.  

Regular Pleskian

You could try to update the plesk install using Code: plesk installer install-panel-updates If that doesnt work then contact support at https://support.plesk.com/hc/en-us  

Host Edition also shows "data.site is null" when opening the domain page. The problem is occurring on all 8 Plesks. I think it was normal when I checked the Host Edition two hours ago.  

Dave W said: You could try to update the plesk install using Code: plesk installer install-panel-updates If that doesnt work then contact support at https://support.plesk.com/hc/en-us Click to expand...

[root@ ~]# plesk installer install-panel-updates Downloading file products.inf3: 0% Downloading file products.inf3: 100% was finished. .... You already have the latest version of product(s) and all the selected components installed. Installation will not continue. [root@ ~]# Click to expand...

let us know what version CLI reports; Code: plesk -v  

MIchael Cockinos

New pleskian.

I'm now getting this same error! What has happened Plesk?  

What version of plesk and OS are you using?  

Dave W said: let us know what version CLI reports; Code: plesk -v Click to expand...

[root@ ~]# plesk -v Product version: Plesk Obsidian 18.0.56.4 OS version: AlmaLinux 8.9 x86_64 Build date: 2023/11/06 15:00 Revision: 7f3265358b91416f035eddb5dfe564171fd100a4 [root@ ~]# Click to expand...

ok the current release of plesk is Plesk Obsidian 18.0.57 Update 2. You need to update to this as I believe there is a hostfix included in a recent update for this issue. Try this: Code: plesk installer install-all-updates  

The message varies depending on the browser you use. The same error message is displayed on the JavaScript console, so it seems to be a JavaScript problem, but the result does not change even after a forced reload. - Safari Right side of assignment cannot be destructured - Firefox data.site is null - Chrome Cannot destructure property 'screenshotUrl' of 'data.site' as it is null.  

just tested the install-all-updates command, it doesnt update plesk. Use the following command to update to the latest release; Code: plesk installer --select-release-latest --upgrade-installed-components  

Dave W said: ok the current release of plesk is Plesk Obsidian 18.0.57 Update 2. You need to update to this as I believe there is a hostfix included in a recent update for this issue. Try this: Code: plesk installer install-all-updates Click to expand...

[root@ ~]# plesk -v Product version: Plesk Obsidian 18.0.57.2 OS version: AlmaLinux 8.9 x86_64 Build date: 2023/11/28 16:00 Revision: d67d6eef84e863abfcdcd912466650cb78b0653d [root@ ~]# Click to expand...

I suggest you contact support at https://support.plesk.com  

This seems to be the same problem. Issue - Right side of assignment cannot be destructured  

Dave W said: I suggest you contact support at https://support.plesk.com Click to expand...

wget https://ext.plesk.com/packages/80591d56-628c-4d24-a685-b805d4d1c589-monitoring/download?2.9.2-433 -O monitoring.zip plesk bin extension -i monitoring.zip Click to expand...

• Dec 5, 2023

Fixed. Thanks  

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TypeError: Right side of assignment cannot be destructured #435

nervusdm commented Sep 24, 2021 • edited

iamhosseindhv commented Sep 25, 2021

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