js 实现asp.net stringbuilder 功能

String.prototype.Trim = function () { return this.replace(/(^[\s　]*)|([\s　]*$)/g, ""); }
String.prototype.Ltrim = function () { return this.replace(/(^[\s　]*)/g, ""); }
String.prototype.Rtrim = function () { return this.replace(/([\s　]*$)/g, ""); }
String.Format = function () {
if (arguments.length == 0)
return "";
if (arguments.length == 1)
return arguments[0];
var reg = /{(\d+)?}/g;
var args = arguments;
var result = arguments[0].replace(
reg,
function ($0, $1) {
return args[parseInt($1) + 1];
}
);
return result;
}
String.prototype.endWith = function (s) {
if (s == null || s == "" || this.length == 0 || s.length > this.length)
return false;
if (this.substring(this.length - s.length) == s)
return true;
else
return false;
return true;
}

String.prototype.startWith = function (s) {
if (s == null || s == "" || this.length == 0 || s.length > this.length)
return false;
if (this.substr(0, s.length) == s)
return true;
else
return false;
return true;
}
String.prototype.bytelength = function () {
var arr = this.match(/[^\x00-\xff]/ig);
return this.length + (arr == null ? 0 : arr.length);
}

String.prototype.empty = function () {
return this.Trim().length == 0;
}
String.prototype.replaceAll = function (findText, repText) {
var raRegExp = new RegExp(findText, "g");
return this.replace(raRegExp, repText);
}

function StringBuilder() {
this.strings = new Array();
}
StringBuilder.prototype.append = function (str) {
this.strings.push(str);
}
StringBuilder.prototype.toString = function () {
if (arguments.length == 0)
return this.strings.join("");
else
return this.strings.join(arguments[0]);
}
StringBuilder.prototype.clear = function () {
this.strings.clear();
}