Node.insertBefore()
Node.insertBefore()
方法將一個節點安插在參考節點之前,作為某個特定父節點之子節點。If the given child is a reference to an existing node in the document, insertBefore()
moves it from its current position to the new position (there is no requirement to remove the node from its parent node before appending it to some other node).
同一個節點並不會同時出現在兩個地方。所以當節點已經有父節點,它會先被移除,然後被插入在新的位置上。The Node.cloneNode()
can be used to make a copy of the node before appending it under the new parent. Note that the copies made with cloneNode
will not be automatically kept in sync.
若參考節點為 null
, 那需插入的節點就會成為特定父節點的最後一個子節點。
If the given child is a DocumentFragment
, the entire contents of the DocumentFragment
are moved into the child list of the specified parent node.
Syntax
Returns
會回傳新加入的子節點。若該值(newNode
)是DocumentFragment
, 則回傳空的 DocumentFragment
。
Example
<div id="parentElement">
<span id="childElement">foo bar</span>
</div>
<script>
// Create the new node to insert
var newNode = document.createElement("span");
// Get a reference to the parent node
var parentDiv = document.getElementById("childElement").parentNode;
// Begin test case [ 1 ] : Exist a childElement --> All working correctly
var sp2 = document.getElementById("childElement");
parentDiv.insertBefore(newNode, sp2);
// End test case [ 1 ]
// Begin test case [ 2 ] : childElement is of Type undefined
var sp2 = undefined; // Not exist a node of id "childElement"
parentDiv.insertBefore(newNode, sp2); // Implicit dynamic cast to type Node
// End test case [ 2 ]
// Begin test case [ 3 ] : childElement is of Type "undefined" ( string )
var sp2 = "undefined"; // Not exist a node of id "childElement"
parentDiv.insertBefore(newNode, sp2); // Generate "Type Error: Invalid Argument"
// End test case [ 3 ]
</script>
insertedNode
被插入的節點,也就是newNode
。parentNode
指定的父節點。newNode
被插入的節點。referenceNode
參考節點。The node before whichnewNode
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
(en-US).
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
Insert an element before the first child element, using the firstChild (en-US) 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
BCD tables only load in the browser
Specifications
Specification |
---|
DOM Standard # dom-node-insertbefore |