Range.setStartBefore()
Range.setStartBefore() 方法相对另一个 Node来设置一个Range 的开始位置. Range的开始节点（focusNode）的父节点，和 referenceNode的父节点是同一个.
Syntax
range.setStartBefore(referenceNode);
Parameters
Example
var range = document.createRange();
var referenceNode = document.getElementsByTagName("div").item(0);
range.setStartBefore(referenceNode);
Specifications
| Specification | Status | Comment |
|---|---|---|
| DOM Range.setStartBefore() |
Living Standard | No change. |
| Document Object Model (DOM) Level 2 Traversal and Range Specification Range.setStartBefore() |
Obsolete | Initial specification. |
Browser compatibility
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