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• 句法
• 范例
• 规范
• 浏览器兼容性
• 相关话题

Node.firstChild read-only property returns the node's first child in the tree, or null if the node has no children. 若节点是 Document , it returns the first node in the list of its direct children.

句法

var childNode = node.firstChild;
					

范例

This example demonstrates the use of firstChild and how whitespace nodes might interfere with using this property.

<p id="para-01">
  <span>First span</span>
</p>
<script>
  var p01 = document.getElementById('para-01');
  console.log(p01.firstChild.nodeName);
</script>
					

In the above, the console will show '#text' because a text node is inserted to maintain the whitespace between the end of the opening <p> and <span> 标签。 任何 whitespace 将创建 #text node, from a single space to multiple spaces, returns, tabs, and so on.

Another #text node is inserted between the closing </span> and </p> 标签。

If this whitespace is removed from the source, the #text nodes are not inserted and the span element becomes the paragraph's first child.

<p id="para-01"><span>First span</span></p>
<script>
  var p01 = document.getElementById('para-01');
  console.log(p01.firstChild.nodeName);
</script>
					

Now the console will show 'SPAN'.

To avoid the issue with node.firstChild 返回 #text or #comment nodes, ParentNode.firstElementChild can be used to return only the first element node. However, node.firstElementChild requires a shim for Internet Explorer 9 and earlier.

规范

规范	状态	注释
DOM The definition of 'Node.firstChild' in that specification.	实时标准	无变化
DOM (文档对象模型) 3 级核心规范 The definition of 'Node.firstChild' in that specification.	过时	无变化
DOM (文档对象模型) 级别 2 核心规范 The definition of 'Node.firstChild' in that specification.	过时	无变化
DOM (文档对象模型) 1 级规范 The definition of 'Node.firstChild' in that specification.	过时	初始定义

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
firstChild	Chrome Yes	Edge 12	Firefox 1	IE Yes	Opera Yes	Safari Yes	WebView Android Yes	Chrome Android Yes	Firefox Android 4	Opera Android Yes	Safari iOS Yes	Samsung Internet Android Yes

图例

完整支持

完整支持

元数据

• 最后修改： Mar 18, 2019

相关话题

1. DOM (文档对象模型)
2. 节点
3. 特性

   1. baseURI
   2. baseURIObject
   3. childNodes
   4. firstChild
   5. isConnected
   6. lastChild
   7. localName
   8. namespaceURI
   9. nextSibling
   10. nodeName
   11. nodePrincipal
   12. nodeType
   13. nodeValue
   14. outerText
   15. ownerDocument
   16. parentElement
   17. parentNode
   18. prefix
   19. previousSibling
   20. rootNode
   21. textContent
4. 方法

   1. appendChild()
   2. cloneNode()
   3. compareDocumentPosition()
   4. contains()
   5. getRootNode()
   6. getUserData()
   7. hasChildNodes()
   8. insertBefore()
   9. isDefaultNamespace()
   10. isEqualNode()
   11. isSameNode()
   12. isSupported()
   13. lookupNamespaceURI()
   14. lookupPrefix()
   15. normalize()
   16. removeChild()
   17. replaceChild()
   18. setUserData()
5. 继承：

   1. EventTarget
6. DOM 相关页面

   1. AbortController
   2. AbortSignal
   3. AbstractRange
   4. Attr
   5. ByteString
   6. CDATASection
   7. CSSPrimitiveValue
   8. CSSValue
   9. CSSValueList
   10. CharacterData
   11. ChildNode
   12. 注释
   13. CustomEvent
   14. DOMConfiguration
   15. DOMError
   16. DOMErrorHandler
   17. DOMException
   18. DOMImplementation
   19. DOMImplementationList
   20. DOMImplementationRegistry
   21. DOMImplementationSource
   22. DOMLocator
   23. DOMObject
   24. DOMParser
   25. DOMPoint
   26. DOMPointInit
   27. DOMPointReadOnly
   28. DOMRect
   29. DOMString
   30. DOMTimeStamp
   31. DOMTokenList
   32. DOMUserData
   33. Document
   34. DocumentFragment
   35. DocumentType
   36. 元素
   37. ElementTraversal
   38. Entity
   39. EntityReference
   40. 事件
   41. EventTarget
   42. HTMLCollection
   43. MutationObserver
   44. NodeFilter
   45. NodeIterator
   46. NodeList
   47. NonDocumentTypeChildNode
   48. ProcessingInstruction
   49. PromiseResolver
   50. 范围
   51. StaticRange
   52. 文本
   53. TextDecoder
   54. TextEncoder
   55. TimeRanges
   56. TreeWalker
   57. TypeInfo
   58. USVString
   59. UserDataHandler
   60. XMLDocument