var chlen = 0;
	$(function(){
		$("textarea").keydown(function(){
			$(this).attr("maxlength","100");
			if(this.value.length>=$(this).attr("maxlength")){
				return;
			}
		});
		$("textarea").keyup(function(){
			chlen = 0;
			if(this.value.length>$(this).attr("maxlength")){
				return;
			}
			$(this).next().next().html("字数限制(<span style='color:red;'>"+this.value.length+"</span>--100)");
			strlen(this.value);
			if(this.value.length<$(this).attr("maxlength")&&chlen != 0){
				$(this).attr("maxlength",eval(100+chlen));
			}
		});
	});
	
	function strlen(str){
	    var len = 0;
	    for (var i=0; i<str.length; i++) { 
	     var c = str.charCodeAt(i); 
	    //字数加1 
	     if ((c >= 0x0001 && c <= 0x007e) || (0xff60<=c && c<=0xff9f)) { 
	       len++; 
	     } 
	     else { 
	   //中文字数加2
	      len+=2;
	   	  chlen++;
	     } 
	    } 
	    return len;
	}