This article is in need of a technical review.

The Node.insertBefore() method inserts the specified node before a reference node as a child of the current node.

Syntax

var insertedNode = parentNode.insertBefore(newNode, referenceNode);

In Mozilla Firefox, if referenceNode is nullnewNode is inserted at the end of the list of child nodes. In Internet Explorer, an undefined value as referenceNode will throw an "Invalid argument" exception, while in Chrome it will throw an "Uncaught TypeError" since it expects both the arguments.

  • insertedNode The node being inserted, that is newNode
  • parentNode The parent of the newly inserted node.
  • newNode The node to insert.
  • referenceNode The node before which newNode is inserted.

Example

<div id="parentElement">
  <span id="childElement">foo bar</span>
</div>

<script>
// Create a new, plain <span> element
var sp1 = document.createElement("span");

// Get a reference to the element, before we want to insert the element
var sp2 = document.getElementById("childElement");
// Get a reference to the parent element
var parentDiv = sp2.parentNode;

// Insert the new element into the DOM before sp2
parentDiv.insertBefore(sp1, sp2);
</script>

There is no insertAfter method. It can be emulated by combining the insertBefore method with nextSibling.

In the previous example, sp1 could be inserted after sp2 using:

parentDiv.insertBefore(sp1, sp2.nextSibling);

If sp2 does not have a next sibling, then it must be the last child — sp2.nextSibling returns null, and sp1 is inserted at the end of the child node list (immediately after sp2).

Example 2

Insert an element before the first child element, using the firstChild property.

// Get a reference to the element in which we want to insert a new node
var parentElement = document.getElementById('parentElement');
// Get a reference to the first child
var theFirstChild = parentElement.firstChild;

// Create a new element
var newElement = document.createElement("div");

// Insert the new element before the first child
parentElement.insertBefore(newElement, theFirstChild);

When the element does not have a first child, then firstChild is null. The element is still appended to the parent, after the last child. Since the parent element did not have a first child, it did not have a last child either. Consequently, the new element is the only element, after insertion.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 1.0 (Yes) (Yes) (Yes) (Yes)
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support ? ? ? ? ?

Specification