js prototype截取字符串函数_javascript技巧

String.prototype.strLen = function() {
var len = 0;
for (var i = 0; i if (this.charCodeAt(i) > 255 || this.charCodeAt(i) }
return len;
}
//将字符串拆成字符，并存到数组中
String.prototype.strToChars = function(){
var chars = new Array();
for (var i = 0; i chars[i] = [this.substr(i, 1), this.isCHS(i)];
}
String.prototype.charsArray = chars;
return chars;
}
//判断某个字符是否是汉字
String.prototype.isCHS = function(i){
if (this.charCodeAt(i) > 255 || this.charCodeAt(i) return true;
else
return false;
}
//截取字符串（从start字节到end字节）
String.prototype.subCHString = function(start, end){
var len = 0;
var str = "";
this.strToChars();
for (var i = 0; i if(this.charsArray[i][1])
len += 2;
else
len++;
if (end return str;
else if (start str += this.charsArray[i][0];
}
return str;
}
//截取字符串（从start字节截取length个字节）
String.prototype.subCHStr = function(start, length){
return this.subCHString(start, start + length);
}
var li= document.getElementsByName("listtitle");
for(var i=0;i{
li[i].innerHTML=li[i].innerHTML.subCHStr(0,28)+"...";
}