请问怎样控制输入字数

看看这个http://topic.csdn.net/u/20100107/10/2d019f0b-bd6a-4c83-aab0-6ed9856f3777.html

window.onload = function() {
document.getElementById("tField").onpaste = function(){
if(this.value.length>10)this.value="...";
}

function LessThan(oTextArea){
//返回文本框字符个数是否符号要求的boolean值
return oTextArea.value.length < oTextArea.getAttribute("maxlength");
}
</script>
<textarea name="comments" id="comments" cols="40" rows="4" maxlength="50" onkeypress="return LessThan(this);"></textarea>

have a try<script type="text/javascript">
window.onload = function() {
    document.getElementById("tField").onbeforepaste  = function(){
        var obj=clipboardData.getData("Text");
        if(this.value.length+obj.length>10)this.value="...";
    }
}
</script>
<input type="text" value="show"id="tField">

谢谢8楼，
只是它要叫两次，为什么？怎样让它只叫一次？
if(this.value.length+obj.length>10){
alert('it is too long');
}

<textarea id=txt name=txt rows='5' cols='60' >txt</textarea>
document.getElementById("txt").onkeyup=document.getElementById("txt").onchange=function(){
//== 函数
}

<!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">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title><script language="javascript">
function inputNumberSet(oIpt, nMin, nMax)
{
  oIpt.oldNum = Number(oIpt.value);
  if(typeof(nMin)=="number")oIpt.nMin = nMin;
  if(typeof(nMax)=="number")oIpt.nMax = nMax;

  oIpt.onkeydown = inputNumKeyDown;
  oIpt.onmousewheel = inputNumWheel;
  oIpt.onkeyup = inputNumKeyUp;
  oIpt.numLimit = inputNumLimit;
}  function inputNumKeyDown(evt)
  {
    var nKeyCode;
    if(typeof(event)=="undefined")
      nKeyCode = evt.keyCode
    else
      nKeyCode = event.keyCode;
    if(nKeyCode==38)
    {
      this.oldNum ++;
      this.value = this.oldNum;
    }
    if(nKeyCode==40)
    {
      this.oldNum --;
      this.value = this.oldNum;
    }
    this.numLimit();
    if((nKeyCode==13)&&typeof(this.fFun)=="function")this.fFun(this);
  }  function inputNumWheel(evt)
  {
    if(typeof(event)=="object")
    {
      if(event.wheelDelta > 0)
      {
        this.oldNum ++;
        this.value = this.oldNum;
      }
      if(event.wheelDelta < 0)
      {
        this.oldNum --;
        this.value = this.oldNum;
      }
      this.numLimit()
    }
  }  function inputNumLimit()
  {
    if((typeof(this.nMin)=="number")&&(this.oldNum<this.nMin))
    {
      this.oldNum    = this.nMin;
      this.value    = this.nMin;
    }
    else
    {
      if((typeof(this.nMax)=="number")&&(this.oldNum>this.nMax))
      {
        this.oldNum = this.nMax;
        this.value  = this.nMax;
      }
    }
    if(typeof(this.onchange)=="function")this.onchange();
  }  function inputNumKeyUp(evt)
  {
    if(this.value.length == 0)
    {
      if((typeof(this.nMin)=="number")&&(this.nMin>0))
      {
        this.value    = this.nMin;
        this.oldNum   = this.nMin;
      }
      else
      {
        this.value    = 0;
        this.oldNum    = 0;
      }
    }
    else
    {
      var nNewNum = Number(this.value);
      if(String(nNewNum) != "NaN")
      {
        this.oldNum    = nNewNum;
      }
      else
      {
        this.value    = this.oldNum;
      }
    }
    this.numLimit();
  }

  function myLoad()
  {
    inputNumberSet(document.getElementById("myInput"), -5, 500)
  }
</script>
</head><body onload="myLoad()">
<p>
  <input type="text" name="myInput" id="myInput"/>
最小-５,最大500。键盘上下可设置。滚轮IE、Chrome等支持</p>
<p> </p>
<p>inputNumberSet(oIpt, nMin, nMax)<br />
oIpt:输入框<br />
  nMin:最小值<br />
    nMax:最大值</p>
</body>
</html>
保存为HTML看看

谢谢上面各位，特别要谢谢shan1119，
可能是我没表达清楚，我要的效果是当字符超过一定数量时，让按钮变灰，使得表单无法提交，
下面是按照13楼的代码写的，这个在ie上好使，可在ff上不行，请大家想想办法，怎样才能在ff上也好使，谢谢！
<script type="text/javascript">
window.onload = function() {
    document.getElementById("txt").onpaste = function(){
        var obj=clipboardData.getData("Text");
        if(this.value.length+obj.length>10){
            alert("Your question is too long!");
            form1.submit.disabled=true
} } }
</script>
<form id=form1>
<textarea id=txt name=txt rows='5' cols='60' >txt</textarea>
<input type=submit name=submit value=submit>
</form>

http://topic.csdn.net/u/20070129/11/E3A25262-FF8D-447C-AC97-117E481D17CE.html
参考一下吧，ff我还没用过

你早说就更简单了 onchange事件中判断下长度就可以了

LZ,你可以试试我这个啊。我在IE，FireFox, Chrome, Opera, Safari上都有测试过啊

谢谢上面各位，这几天有事，没及时结帖，15楼的代码以后有时间一定好好钻研一下，最后我采用的方案是：
<script>
function len_over(){
    txt=document.getElementById("txt")
    if(txt.value.length>10){
        alert("it is too long!");
        form1.submit.disabled=true;
}}
</script>
<form id=form1>
<textarea id=txt name=txt rows=5 cols=60 onfocus={form1.submit.disabled=false;}>
<input type=submit name=submit value=submit onclick=len_over()>
</form>这个在ie上很好用，给了提示，按钮灰了，也不离开原页面，txt中的东西还在，
在ff上，转到了action指定的页面，尽管数据没被处理，也可以再转回来，但毕竟要多几行代码，给人感觉不好，
再次谢谢大家，有好的办法请告诉我，谢谢！

调试易

请问怎样控制输入字数

解决方案 »