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常用的Javascript限制輸入字元數代碼

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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.111cn.net/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.111cn.net/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css教程" media="screen">
body{ margin:0px; padding:0px;}
div{ width:400px; margin:0px auto;}
div h3{ background:#CCCCCC; font-size:14px; font-weight:bold; text-align:center; line-height:22px; margin:6px 0px; padding:0px;}
div textarea{ width:388px; height:120px; border:#999999 1px solid; margin:0px; padding:0px; font-size:12px; padding:5px; line-height:16px;}
div p{ font-size:12px; margin:0px; line-height:22px;}
div p span{ color:#FF6600; font-weight:bold;}
</style>
<title>Javascript限制文字框輸入的最大字元數</title>
</head>

<body>
<div>
<h3>字元數測試</h3>
<textarea rows="20" cols="50" onkeypress="return checkMaxLength(this,20)"></textarea>
<p>最多<span>20</span>個字元。</p>
</div>

<script type="text/javascript教程">
function checkMaxLength(oTextArea,maxLength){
   return oTextArea.value.length!=maxLength;
}
</script>
</body>
</html>

方案二

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.111cn.net/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.111cn.net/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css" media="screen">
body{ margin:0px; padding:0px;}
div{ width:400px; margin:0px auto;}
div h3{ background:#CCCCCC; font-size:14px; font-weight:bold; text-align:center; line-height:22px; margin:6px 0px; padding:0px;}
div textarea{ width:388px; height:120px; border:#999999 1px solid; margin:0px; padding:0px; font-size:12px; padding:5px; line-height:16px;}
div p{ font-size:12px; margin:0px; line-height:22px;}
div p span{ color:#FF6600; font-weight:bold;}
</style>
<title>Javascript限制文字框輸入的最大字元數</title>
</head>

<body>
<div>
<h3>字元數測試</h3>
<textarea rows="20" cols="50" onkeyup="checkMaxLength(this,20)" onpaste="checkMaxLength(this,20)"></textarea>
<p>最多<span>20</span>個字元。</p>
</div>

<script type="text/javascript">
function checkMaxLength(area, maxLength) {
    if (area.value.length >maxLength) {
        area.value = area.value.substr(0, maxLength);
    }
}
</script>
</body>
</html>

方案三

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.111cn.net/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.111cn.net/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css" media="screen">
body{ margin:0px; padding:0px;}
div{ width:400px; margin:0px auto;}
div h3{ background:#CCCCCC; font-size:14px; font-weight:bold; text-align:center; line-height:22px; margin:6px 0px; padding:0px;}
div textarea{ width:388px; height:120px; border:#999999 1px solid; margin:0px; padding:0px; font-size:12px; padding:5px; line-height:16px;}
div p{ font-size:12px; margin:0px; line-height:22px;}
div p span{ color:#FF6600; font-weight:bold;}
</style>
<title>Javascript限制文字框輸入的最大字元數</title>
</head>

<body>
<div>
<h3>字元數測試</h3>
<textarea rows="20" cols="50" onkeyup="checkMaxLength(this,20)" onpaste="checkMaxLength(this,20)"></textarea>
<p>最多<span>20</span>個字元，一個漢字2個字元。</p>
</div>

<script type="text/javascript">
function checkMaxLength(area, maxLength) {
      var currentStr="";
      for(var i=0,len=area.value.length;i<len;i++) {
           currentStr+=area.value.charAt(i);
           if(getCharLength(currentStr)>maxLength){
                  area.value=area.value.substr(0,i);
                   return;
           }
     }
}

function getCharLength(str){
     var charLen=0;
  for(var i=0,len=str.length;i<len;i++){
       if(str.charCodeAt(i)>255){
        charLen+=2;
    }else{
        charLen+=1;
    } 
  }
  return charLen;
}
</script>
</body>
</html>

方案三

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.111cn.net/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.111cn.net/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css" media="screen">
body{ margin:0px; padding:0px;}
div{ width:400px; margin:0px auto;}
div h3{ background:#CCCCCC; font-size:14px; font-weight:bold; text-align:center; line-height:22px; margin:6px 0px; padding:0px;}
div textarea{ width:388px; height:120px; border:#999999 1px solid; margin:0px; padding:0px; font-size:12px; padding:5px; line-height:16px;}
div p{ font-size:12px; margin:0px; line-height:22px;}
div p span{ color:#FF6600; font-weight:bold;}
</style>
<title>Javascript限制文字框輸入的最大字元數</title>
</head>

<body>
<div>
<h3>字元數測試</h3>
<textarea rows="20" cols="50" onkeyup="checkMaxLength(this,20)" onpaste="return false;"></textarea>
<p>最多<span>20</span>個字元，一個漢字2個字元，你還可以輸入<span>20</span>字元</p>
</div>

<script type="text/javascript">
var s=document.getElementsByTagName("span")[1];
function checkMaxLength(area, maxLength) {
      var currentStr="";
   if(area.value.length==0){s.innerHTML=maxLength;}
      for(var i=0,len=area.value.length;i<len;i++) {
           currentStr+=area.value.charAt(i);
           if(getCharLength(currentStr)>maxLength){
                  area.value=area.value.substr(0,i);
                   return;
           }else{
             s.innerHTML=maxLength-getCharLength(currentStr);
     }
     }
}

function getCharLength(str){
     var charLen=0;
  for(var i=0,len=str.length;i<len;i++){
       if(str.charCodeAt(i)>255){
        charLen+=2;
    }else{
        charLen+=1;
    } 
  }
  return charLen;
}
</script>
</body>
</html>

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