In JavaScript, what is the best way to convert a NodeList to an array?

The DOM method document.querySelectorAll() (and a few others) return a NodeList.

To operate on the list, e.g. using forEach(), the NodeList must first be converted to an Array.

What's the best way to convert the NodeList to a开发者_如何学JAVAn Array?

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With ES6 you can simply do:

const spanList = [...document.querySelectorAll("span")];

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With ES6 you can use Array.from(myNodeList). Then use your favourite array method.

var myNodeList = document.querySelectorAll('.my-selector');

// ALT 1
Array.from(myNodeList).forEach(function(el) {
  console.log(el);
});

Use an ES6 shim to make this work in older browsers too.

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If you are using a transpiler (for example Babel) there are two more alternatives:

var myNodeList = document.querySelectorAll('.my-selector');

// ALT 2
for (var el of myNodeList) {
  el.classList.add('active'); // or some other action
}

// ALT 3
[...myNodeList].forEach((el) => {
  console.log(el);
});

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You can convert it to an array by using the slice method from the Array prototype:

var elList = document.querySelectorAll('.viewcount');
elList = Array.prototype.slice.call(elList, 0);

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Furthermore, if all you need is forEach, you can invoke that from the Array prototype, without coercing it to an array first:

var elList = document.querySelectorAll('.viewcount');
Array.prototype.forEach.call(elList, function(el) {
    console.log(el);
});

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In ES6, you can use the new Array.from function to convert it to an array:

Array.from(elList).forEach(function(el) {
    console.log(el);
});

This is currently only in bleeding edge browsers, but if you're using a polyfill service you will have access to this function across the board.

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If you're using an ES6 transpiler, you can even use a for..of loop instead:

for (var element of document.querySelectorAll('.some .elements')) {
  // use element here
}

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Why convert? - just call function of Array directly on element collection ;)

[].forEach.call( $('a'), function( v, i) {
    // do something
});

assuming $ is your alias for querySelectorAll, of course

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edit: ES6 allows for even shorter syntax [...$('a')] (works in Firefox only, as of May 2014)

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2020 update: nodeList.forEach() is now an official standard and supported in all current browsers.

Older browsers can use the polyfill below.

To operate on the list in javascript, e.g. using forEach(), the NodeList must be converted to an Array.

That's not true. .forEach() works in current browsers. If it's missing, you can use a polyfill to add .forEach() from Array to NodeList and it works fine:

if ( ! NodeList.prototype.forEach ) {
  NodeList.prototype.forEach = Array.prototype.forEach;
}

You can now run:

myNodeList.forEach(function(node){...})

To iterate over NodeLists just like Arrays.

This produces much shorter and cleaner code than .call() everywhere.

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Does it have to be forEach? You could simply use a for loop to iterate over the list:

for (var i = 0; i < elementList.length; i++) {
    doSomethingWith(elementlist.item(i));
}

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Well, this works for me too:

const elements = Object.values( document.querySelector(your selector here) )

Object.values() returns Array of values of given object. NodeList is object, as is everything in JS.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values

But it's not compatible with IE, so i guess Array.prototype.*array_method*.call(yourNodeList) is the best option. With this you can invoke any array method on your NodeList

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I use the following because I think it's easiest to read:

const elements = document.getElementsByClassName('element');
[...elements].forEach((element) => {
   // code
});

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Assuming elems is a nodeList:

var elems = document.querySelectorAll('select option:checked');

then it can be turned into an array as follows:

var values = [].map.call(elems, function(obj) {
  return obj.value;
});

Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map#Example:_using_map_generically_querySelectorAll

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ES6 allows cool ways like var nodeArray = Array.from(nodeList) but my favorite one is the new spread operator.

var nodeArray = Array(...nodeList);

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That worked with me in ES6

lets assume you have nodelist like that

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</ul>


const items = Array.from(document.querySelectorAll('[data-time]'));

console.log(items);

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TypeScript version:

const allDayElements: Element[] = [].slice.call(document.querySelectorAll('span'));