JS控制输入字符长度


<script language="JavaScript"> 
    <!-- 
    function CutStrLength(str,Ilength)
    {
        var tmp=0;
        var len=0;
        var okLen=0
        for(var i=0;i<Ilength;i++)
        {
            if(str.charCodeAt(i)>255)
                tmp+=2
            else
                len+=1
            okLen+=1
            if(tmp+len==Ilength)
            {
                return (str.substring(0,okLen));
                break;
            }
            if(tmp+len>Ilength)
            {
                return (str.substring(0,okLen-1)+"");
                break;
            }
        }
    }
    function checkFieldLength(fieldName,fieldDesc,fieldLength)
    {
        var str=document.getElementById(fieldName).value;
        var theLen=0;
        var teststr='';
        for(i=0;i<str.length;i++)
        {
            teststr=str.charAt(i);
            if(str.charCodeAt(i)>255)
            theLen=theLen+2;
            else
            theLen=theLen+1;
        }
        document.getElementById('showMsg').innerText=theLen;
        if(theLen>fieldLength)
        {
            document.getElementById('showMsg').innerText=fieldDesc;
            //alert(fieldDesc+" 的字段长度超过规定长度！");
            //document.getElementById(fieldName).focus();
            document.getElementById(fieldName).value=CutStrLength(str,fieldLength);
            return false;
        }
        else
        {
            return true;
        }
    }
    //-->
    </script>

</head>
<body>
    <form method="POST" action="">
        <textarea id="testArea" name="testArea" rows="3" cols="22" onkeyup="checkFieldLength('testArea', '超过允许输入的字符个数', 20);"
            onchange="checkFieldLength('testArea', '超过允许输入的字符个数', 20);"></textarea>
        <div id="testInfo">
            已经输入:<span id="showMsg"></span></div>
    </form>
</body>
</html>
JS控制输入字符长度

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