js动态加载数据到文本框指定的位置

html代码

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

<script type="text/javascript"
    src="111.js"></script>

  <form   id="form1"   action=""   onsubmit=""   method="post"   enctype="text/plain">   
  <p> 
          <textarea   name="tarea"   rows=""   cols=""   style="300px;height:120px;" 
          onclick="setCaret(this);" 
          >哈哈按钮 大阿萨德发按时</textarea> 
        <br/><br/> 
        <input   type="text"   name="textfield"   style="220px;"   value="插入FireFox"/> 
        <br/> 
        <input   type="button"   value="插入" onclick="insertAtCaret(this.form.tarea,this.form.textfield.value);"/> 
  </p> 
  </form>
</html>

js代码，名为111.js

    function setCaret(textObj) {
                if (textObj.createTextRange) {
                    textObj.caretPos = document.selection.createRange().duplicate();
                }
            }
            function insertAtCaret(textObj, textFeildValue) {
                if (document.all) {
                    if (textObj.createTextRange && textObj.caretPos) {
                        var caretPos = textObj.caretPos;
                        caretPos.text = caretPos.text.charAt(caretPos.text.length - 1) == '   ' ? textFeildValue + '   ' : textFeildValue;
                    } else {
                        textObj.value = textFeildValue;
                    }
                } else {
                    if (textObj.setSelectionRange) {
                        var rangeStart = textObj.selectionStart;
                        var rangeEnd = textObj.selectionEnd;
                        var tempStr1 = textObj.value.substring(0, rangeStart);
                        var tempStr2 = textObj.value.substring(rangeEnd);
                        textObj.value = tempStr1 + textFeildValue + tempStr2;
                    } else {
                        alert("This   version   of   Mozilla   based   browser   does   not   support   setSelectionRange");
                    }
                }
            }

插入后效果