ParentNode.firstElementChild

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ParentNode.firstElementChild 介面會會返回 ParentNode的第一個子元素(唯讀) ,如果該節點沒有子節點則返回null

This property was initially defined in the ElementTraversal pure interface. As this interface contained two distinct set of properties, one aimed at Node that have children, one at those that are children, they have been moved into two separate pure interfaces, ParentNode and ChildNode. In this case, firstElementChild moved to ParentNode. This is a fairly technical change that shouldn't affect compatibility.

語法

var element = node.firstElementChild; 

範例

<ul id="foo">
  <li>First  (1)</li>
  <li>Second (2)</li>
  <li>Third  (3)</li>
</ul>

<script>
var foo = document.getElementById('foo');
// yields: First  (1)
console.log(foo.firstElementChild.textContent);
</script>

適用於IE8, IE9 和 Safari的Polyfill

// Overwrites native 'firstElementChild' prototype.
// Adds Document & DocumentFragment support for IE9 & Safari.
;(function(constructor) {
    if (constructor &&
        constructor.prototype &&
        constructor.prototype.firstElementChild == null) {
        Object.defineProperty(constructor.prototype, 'firstElementChild', {
            get: function() {
                var node, nodes = this.childNodes, i = 0;
                while (node = nodes[i++]) {
                    if (node.nodeType === 1) {
                        return node;
                    }
                }
                return null;
            }
        });
    }
})(window.Node || window.Element);

規範

Specification Status Comment
DOM
The definition of 'ParentNode.firstElementChild' in that specification.
Living Standard Split the ElementTraversal interface in ChildNode and ParentNode. This method is now defined on the latter.
The Document and DocumentFragment implemented the new interfaces.
Element Traversal Specification
The definition of 'ElementTraversal.firstElementChild' in that specification.
Obsolete Added its initial definition to the ElementTraversal pure interface and use it on Element.

瀏覽器相容性

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
firstElementChildChrome Full support 1Edge ? Firefox Full support 3.5IE Full support 9Opera Full support 10Safari Full support 4WebView Android Full support YesChrome Android Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes
Support on Document and DocumentFragment
Experimental
Chrome Full support 29Edge ? Firefox Full support 25IE No support NoOpera Full support 16Safari No support NoWebView Android Full support YesChrome Android Full support YesFirefox Android ? Opera Android ? Safari iOS No support NoSamsung Internet Android Full support Yes

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.

參見