input 和 textarea 输入框最大文字限制插件

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/* input 和 textarea 最大文字限定插件  * 修改版, 一个中文表示1一个字, 一个英文半个字;  * TextLimit - jQuery plugin for counting and limiting characters for input and textarea fields  *  * pass '-1' as speed if you don't want the char-deletion effect. (don't just put 0)  * Example: jQuery("Textarea").textlimit('span.counter',256)  *  * $Version: 2009.07.25 +r2  * Copyright (c) 2009 Yair Even-Or  * vsync.design@gmail.com */ ; String.prototype.getBytes = function () {     var cArr = this.match(/[^\x00-\xff]/ig);     return this.length + (cArr == null ? 0 : cArr.length); }; (function(jQuery) {     jQuery.fn.textlimit=function(counter_el, thelimit, speed) {         var charDelSpeed = speed || 15;         var toggleCharDel = speed != -1;         var toggleTrim = true;         var that = this[0];         var isCtrl = false;         updateCounter();                   function updateCounter(){             if(typeof that == "object")                 jQuery(counter_el).text(thelimit - Math.ceil(that.value.getBytes()/2));         };                   this.keydown (function(e){             if(e.which == 17) isCtrl = true;             var ctrl_a = (e.which == 65 && isCtrl == true) ? true : false; // detect and allow CTRL + A selects all.             var ctrl_v = (e.which == 86 && isCtrl == true) ? true : false; // detect and allow CTRL + V paste.             // 8 is 'backspace' and 46 is 'delete'             if( this.value.length >= thelimit && e.which != '8' && e.which != '46' && ctrl_a == false && ctrl_v == false)                 e.preventDefault();         })         .keyup (function(e){             updateCounter();             if(e.which == 17)                 isCtrl=false;               if( this.value.length >= thelimit && toggleTrim ){                 if(toggleCharDel){                     // first, trim the text a bit so the char trimming won't take forever                     // Also check if there are more than 10 extra chars, then trim. just in case.                     if ( (this.value.length - thelimit) > 10 )                         that.value = that.value.substr(0,thelimit+100);                     var init = setInterval                         (                             function(){                                 if( that.value.length <= thelimit ){                                     init = clearInterval(init); updateCounter()                                 }                                 else{                                     // deleting extra chars (one by one)                                     that.value = that.value.substring(0,that.value.length-1); jQuery(counter_el).text(Math.ceil(that.value.getBytes()/2));                                 }                             } ,charDelSpeed                         );                 }                 else this.value = that.value.substr(0,thelimit);             }         });               }; })(jQuery);