Summary

Inserts the specified node before a reference element as a child of the current node.

Syntax

var insertedElement = parentElement.insertBefore(newElement, referenceElement);

If referenceElement is null, newElement is inserted at the end of the list of child nodes.

• insertedElement The node being inserted, that is newElement
• parentElement The parent of the newly inserted node.
• newElement The node to insert.
• referenceElement The node before which newElement is inserted.

Example

 <html>

 <head>
 <title>Gecko DOM insertBefore test</title>
 </head>

 <body>
 <div>
   <span id="childSpan">foo bar</span>
 </div>

 <script type="text/javascript">
 // create an empty element node
 // without an ID, any attributes, or any content
 var sp1 = document.createElement("span");

 // give it an id attribute called 'newSpan'
 sp1.setAttribute("id", "newSpan");

 // create some content for the newly created element.
 var sp1_content = document.createTextNode("This is a new span element. ");

 // apply that content to the new element
 sp1.appendChild(sp1_content);

 var sp2 = document.getElementById("childSpan");
 var parentDiv = sp2.parentNode;

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

 </body>
 </html>

There is no insertAfter method, however it can be emulated using a combination of insertBefore and nextSibling.

From the above example, sp1 could be inserted after sp2 using:

parentDiv.insertBefore(sp1, sp2.nextSibling);

If sp2 does not have a next sibling it must be the last child—sp2.nextSibling will return null so sp1 will be inserted at the end of the child nodes list (i.e. immediately after sp2).

Example 2

Insert element as first child before existing firstChild.

// tag the parent nodes first child
var parentDiv = document.getElementById("parent").firstChild;

// create the new element to insert
var dv1 = document.createElement("div");

// give the new element an id
dv1.setAttribute("id", "newDiv");

// insert the new element into the DOM before the existing first child
parentDiv.parentNode.insertBefore(dv1, parentDiv);

Specification

insertBefore