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/DOM

ChildNode.before

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The ChildNode.before method inserts a set of Node or DOMString objects in the children list of this ChildNode's parent, just before this ChildNode. DOMString objects are inserted as equivalent Text nodes.

Syntax

[Throws, Unscopable] 
void ChildNode.before((Node or DOMString)... nodes);

Parameters

nodes
A set of Node or DOMString objects to insert.

Exceptions

Examples

Inserting an element

var parent = document.createElement("div");
var child = document.createElement("p");
parent.appendChild(child);
var span = document.createElement("span");

child.before(span);

console.log(parent.outerHTML);
// "<div><span></span><p></p></div>"

Inserting text

var parent = document.createElement("div");
var child = document.createElement("p"); 
parent.appendChild(child);

child.before("Text"); 

console.log(parent.outerHTML);
// "<div>Text<p></p></div>"

Inserting an element and text

var parent = document.createElement("div");
var child = document.createElement("p"); 
parent.appendChild(child); 
var span = document.createElement("span");

child.before(span, "Text"); 

console.log(parent.outerHTML);
// "<div><span></span>Text<p></p></div>"

ChildNode.before() is unscopable

The before() method is not scoped into the with statement. See Symbol.unscopables for more information.

with(node) { 
  before("foo");
}
// ReferenceError: before is not defined 

Polyfill

You can polyfill the before() method in Internet Explorer 9 and higher with the following code:

// from: https://github.com/jserz/js_piece/blob/master/DOM/ChildNode/before()/before().md
(function (arr) {
  arr.forEach(function (item) {
    if (item.hasOwnProperty('before')) {
      return;
    }
    Object.defineProperty(item, 'before', {
      configurable: true,
      enumerable: true,
      writable: true,
      value: function before() {
        var argArr = Array.prototype.slice.call(arguments),
          docFrag = document.createDocumentFragment();
        
        argArr.forEach(function (argItem) {
          var isNode = argItem instanceof Node;
          docFrag.appendChild(isNode ? argItem : document.createTextNode(String(argItem)));
        });
        
        this.parentNode.insertBefore(docFrag, this);
      }
    });
  });
})([Element.prototype, CharacterData.prototype, DocumentType.prototype]);

Specification

Specification Status Comment
DOM
The definition of 'ChildNode.before()' in that specification.
Living Standard Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Edge Opera Safari
Basic support 54.0 49 (49) No support No support 39.0 No support
Feature Android Webview Firefox Mobile (Gecko) IE Mobile Edge Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support ? 49.0 (49) No support ? 39.0 No support 54.0

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/ChildNode/before