DOM range对象

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The Range object represents a fragment of a document that can contain nodes and parts of text nodes in a given document.

A range can be created using the createRange method of the Document object. Range objects can also be retrieved by using thegetRangeAt method of the Selection object.

Range.setStart方法

If the startNode is a Node of type Text, Comment, or CDATASection, then startOffset is the number of characters from the start of startNode. For other Node types,startOffset is the number of child nodes between the start of the startNode.

Setting the start point below (further down in the document) than the end point will throw an NS_ERROR_ILLEGAL_VALUE exception.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"        "http://www.w3.org/TR/html4/loose.dtd"><html><head>    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />    <title>range.collapsed实例探讨</title></head><body>    <div id="div1">        <p>这个是第一段话</p>        <p>这个是第二段话</p>        <p>这个是第三段话</p>    </div>    <script type="text/javascript">        var range = document.createRange();        /*        //startNode是Text 结点情况        var startNode = document.getElementsByTagName("p").item(0).firstChild;        var startOffset = 0;        var endOffset = startNode.length-1;        range.setStart(startNode,startOffset);        range.setEnd(startNode,endOffset);        */

        //startNode是element 结点情况        var startNode = document.getElementById("div1");        var startOffset = 0;        var endOffset = startNode.children.length-1;        range.setStart(startNode,startOffset);        range.setEnd(startNode,endOffset);        range.selectNode(startNode.children[1]);        var doc = range.cloneContents();

        document.body.appendChild(doc);    </script></body></html>