【转载】 input 和 textarea 最大文字限定插件

/* 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);