文本选择 求助！

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<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>光标位置</title>
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点击 TextArea 实现光标定位                                    
                                    
<p>                                    
<textarea rows="7" cols="49" id="box" onclick=tellPoint()>我怕来不及我要抱着你，直到感觉你的绉纹有了岁月的痕迹，直到视线变得模糊直到不能呼吸
为了你我愿意
动也不能动也要看着你，直到感觉你的发线有了白雪的痕迹，直到肯定你是真的直到失去力气让我们形影不离
如果全世界我也可以放弃，至少还有你值得我去珍惜而你在这里就是生命的奇迹
也许全世界我也可以忘记，就是不愿意失去你的消息你掌心的痣我总记得在哪里
我们好不容易我们身不由已，我怕时间太快不够将你看仔细，我怕时间太慢日夜担心失去你恨不得一夜之间白头永不分离
</textarea>       
     
<script>     
     
function movePoint()     
{     
        var pn = parseInt(pnum.value);     
             
        if(isNaN(pn))     
                return;     
             
        var rng = box.createTextRange(); 
                     
        rng.moveStart("character",pn);     
             
        rng.collapse(true);             
             
        rng.select();     
             
        returnCase(rng)             
                     
}     
     
function tellPoint()     
{     
        var rng = event.srcElement.createTextRange();        
     
        rng.moveToPoint(event.x,event.y);             
        rng.moveStart("character",-event.srcElement.value.length)             
             
        pnum.value = rng.text.length     
             
        returnCase(rng)     
}     
     
     
function returnCase(rng)     
{     
        bh.innerText = rng.boundingHeight;     
        bl.innerText = rng.boundingLeft;     
        bt.innerText = rng.boundingTop;     
        bw.innerText = rng.boundingWidth;     
        ot.innerText = rng.offsetTop;     
        ol.innerText = rng.offsetLeft;     
        t.innerText  = rng.text;     
}     
     
     
function selectText(sp,ep)     
{     
        sp = parseInt(sp)     
        ep = parseInt(ep)     
             
        if(isNaN(sp)||isNaN(ep))     
                return;     
                     
        var rng = box.createTextRange();     
             
        rng.moveEnd("character",-box.value.length)     
        rng.moveStart("character",-box.value.length)     
             
        rng.collapse(true);     
             
        rng.moveEnd("character",ep)     
        rng.moveStart("character",sp)     
             
        rng.select();     
             
        returnCase(rng);     
}     var rg = box.createTextRange();
     
function findText(tw)     
{     
        if(tw=="")     
                return;        
             
        var sw = 0;     
             
        if(document.selection)     
        {     
                sw = document.selection.createRange().text.length;     
        }             
             
        rg.moveEnd("character",box.value.length);     
             
        rg.moveStart("character",sw);                                  
        if(rg.findText(tw))             
        {     
                rg.select();                 returnCase(rg);           
        }        
        
        if(rg.text!=tw)
        {
                alert("已经搜索完了")
                rg = box.createTextRange()
        }
                     
}     
     
</script>                                  
</p>                                    
<p></p>                                    
光标位置：<input type="text" value="0" id="pnum" size="8"> <input type="button" onclick="movePoint()" value="移动光标到指定位置">                                 
<p></p>                               
选择指定范围：<input type="text" size="9" id="sbox"> -- <input type="text" size="9" id="ebox"> <input type="button" onclick="selectText(sbox.value,ebox.value)" value="选择">                                
<p></p>                    
选择查找字符 ：<input type="text" value="" id="cbox" size="8"> <input type="button" onclick="findText(cbox.value)" value="查找下一个并选择">                                 
                    
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    <td width="217">boundingTop:&nbsp;<span id="bt"></span></td>                              
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    <td width="217">boundingLeft:&nbsp;<span id="bl"></span></td>                              
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    <td width="217">offsetLeft:&nbsp;<span id="ol"></span> </td>                              
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    <td width="217">offsetTop:&nbsp;<span id="ot"></span> </td>                              
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    <td width="217">text:&nbsp;<span style="position: absolute; z-index: 10" id="t"></span> </td>                              
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