通过javascript在光标处插入文本


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<!--http://community.csdn.net/Expert/TopicView3.asp?id=5649731-->
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
  <title>Insert Text into TextBox at Cursor Position by Javascript</title>
  <script type="text/javascript">
  var cursPos; // 窗口全局变量,保存目标 TextBox 的最后一次活动光标位置
  function insertText() {  
    var txt1 = document.getElementById("Text1");
    var txt2 = document.getElementById("Text2");    
    //debugger;
    if(!cursPos) TraceCursorPosition(txt2); // 获取光标位置    
    txt2.value = txt2.value.slice(0, cursPos.start) +
      txt1.value + txt2.value.slice(cursPos.end)
  } 
  // 跟踪光标位置
  function TraceCursorPosition(obj)
  {    
    //debugger;
    cursPos = $CursorPosition(obj);
  }
  // 返回光标所在位置
  /**//*
   * source: http://blog.csdn.net/liujin4049/archive/2006/09/19/1244065.aspx
   * source: http://www.devdao.com
   * acknowledges for Marshall
   * example:
   * var myTextBox = document.getElementById("MyTextBoxID");
   * var cursPos = $CursorPosition(myTextBox);
   * alert(cursPos.item[0] + " " + cursPos.item[1]);
   * // OR
   * alert(cursPos.start + " " + cursPos.end);  
  */
  function $CursorPosition(textBox){    
    var start = 0, end = 0;
    //如果是Firefox(1.5)的话,方法很简单
    if(typeof(textBox.selectionStart) == "number"){
      start = textBox.selectionStart;
      end = textBox.selectionEnd;
    }
    //下面是IE(6.0)的方法,麻烦得很,还要计算上'n'
    else if(document.selection) {
      var range = document.selection.createRange();
      if(range.parentElement().id == textBox.id) {
        // create a selection of the whole textarea
        var range_all = document.body.createTextRange();
        range_all.moveToElementText(textBox);
        //两个range,一个是已经选择的text(range),一个是整个textarea(range_all)
        //range_all.compareEndPoints()比较两个端点,如果range_all比range更往左(further to the left),则        
        //返回小于0的值,则range_all往右移一点,直到两个range的start相同。
        // calculate selection start point by moving beginning of range_all to beginning of range
        for (start=0; range_all.compareEndPoints("StartToStart", range) < 0; start++)
          range_all.moveStart('character', 1);
        // get number of line breaks from textarea start to selection start and add them to start
        // 计算一下n
        for (var i = 0; i <= start; i ++) {
          if (textBox.value.charAt(i) == 'n')
            start++;
        }
        // create a selection of the whole textarea
        var range_all = document.body.createTextRange();
        range_all.moveToElementText(textBox);
        // calculate selection end point by moving beginning of range_all to end of range
        for (end = 0; range_all.compareEndPoints('StartToEnd', range) < 0; end ++) {
          range_all.moveStart('character', 1);
        }
        // get number of line breaks from textarea start to selection end and add them to end
        for (var i = 0; i <= end; i ++) {
          if (textBox.value.charAt(i) == 'n')
            end ++;
        }
      }
    }
    //return [start, end]; // 包括选中区域的起始位置
    // modified to return as Object
    return {"start": start, "end": end, "item": [start, end]};
  }
  </script>
</head>
<body>
  input :<input id="Text1" type="text" /><input id="Button1" type="button" value="Insert" onclick="insertText()" /><br />
  output:<textarea id="Text2" cols="40" rows="10" onkeydown="TraceCursorPosition(this)" onkeypress="TraceCursorPosition(this)" onfocus="TraceCursorPosition(this)" onselect="TraceCursorPosition(this)" onmouseover="TraceCursorPosition(this)" onmousedown="TraceCursorPosition(this)">hello world!</textarea><br />
</body>
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