js substr支持中文截取函数代码(中文是双字节)_javascript技巧

复制代码 代码如下:

复制代码 代码如下:

function mb_strlen(str) {
 var len = 0;
 for(var i = 0; i   len += str.charCodeAt(i) 255 ? (charset == 'utf-8' ? 3 : 2) : 1;
 }
 return len;
}

<script type="text/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> <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);"> <div id="testInfo"> 已经输入:<span id="showMsg"></span> </div>