将html文本输入限制为特定的字节数？ [英] Limit html text input to a particular number of bytes?

问题描述

使用HTML5（或者更不用说JavaScript）可以限制输入的最大长度为特定字节数量？

我意识到我可以限制为多个字符：

 < input type =文字maxlength =4/> 
  

但这还不够好，因为我最多可以输入四个双字节字符。 p>

显然，我正在验证这个服务器端，但我也希望在浏览器端也能这样。

编辑：为了清楚起见，我希望能够支持UTF-8。对不起@elclanrs。

解决方案

这个脚本有一些可以清理的UX小故障，但它确实完成了基本任务概述，当我测试它在铬：

 < input id = myinp /> 
 
 
< script> //绑定处理程序输入：
 myinp.onkeypress = myinp.onblur = myinp.onpaste = function vld（e）{
 var inp = e.target; 
 //在文本中使用的字节数：
 if（encodeURIComponent（inp.value）.replace（/％[AF \d] {2,6} / g，'U'）。length> ; 4）{
 //如果字节太多，请尝试拒绝：
 e.preventDefault; 
 inp.value = inp.val || inp.value; 
返回false; 
} 
 //备份最后一次已知的良好值：
 inp.val = inp.value; 
} 
 
< / script> 
  

Using HTML5 (or less preferably JavaScript) is it possible to limit the maximum length of an input to a particular number of bytes?

I realise that I can limit to a number of characters with:

<input type="text" maxlength="4" />

But that's not good enough because I can input up to four two-byte chars in it.

Obviously I am validating this server-side, but I would like this on the browser-side too.

Edit: Just to be clear, I do wish to be able to support UTF-8. Sorry @elclanrs.

解决方案

this script has a couple minor UX glitches that can be cleaned up, but it does accomplish the basic task outlined when i tested it in chrome:

<input id=myinp />


<script> // bind handlers to input:
   myinp.onkeypress=myinp.onblur=myinp.onpaste= function vld(e){
     var inp=e.target;
     // count bytes used in text:
     if( encodeURIComponent(inp.value).replace(/%[A-F\d]{2,6}/g, 'U').length > 4){
        // if too many bytes, try to reject:
        e.preventDefault;
        inp.value=inp.val||inp.value;
        return false;
     }
     // backup last known good value:
    inp.val=inp.value;
   }

</script>

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