String 的扩展和 stringBuilder 也是很有意思的

[lzpong]

/*string 的扩展*/
String.prototype.toInt=function(){return parseInt(this);}
String.prototype.toFloat=function(){return parseFloat(this);}
String.prototype.trim = function (s) {
  if (s) return this.trimEnd(s) .trimStart(s);
  return this.replace(/(^[ \t\n\r]*)|([ \t\n\r]*$)/g, '');
}
String.prototype.trimEnd = function (s) {
  if (this.endsWith(s))
    return this.substring(0, this.length - s.length);
  return this;
}
String.prototype.trimStart = function (s) {
  if (this.startsWith(s))
    return this.slice(s.length);
  return this;
}
String.prototype.startsWith = function (str) {
  return (this.indexOf(str) == 0);
}
String.prototype.endsWith = function (str) {
  return (str.length <= this.length && this.substr(this.length - str.length, str.length) == str);
}
String.prototype.remove = function (start, length) {
  var str1 = this.substring(0, start);
  var str2 = this.substring(start + length, this.length);
  return str1 + str2;
}
String.prototype.insert = function (index, str) {
  var str1 = this.substring(0, index);
  var str2 = this.substring(index, this.length);
  return str1 + str + str2;
}
String.prototype.hashCode = function () {
  var h = 31;
  var i = 0;
  var l = this.length;
  while (i < l) h ^= (h << 5) + (h >> 2) + this.charCodeAt(i++);
  return h;
}
String.format = function (fmt) {
  for (var i = 1; i < arguments.length; i++) {
    var reg = new RegExp('\\{' + (i - 1) + '\\}', 'ig');
    fmt = fmt.replace(reg, arguments[i]);
  }
  return fmt;
}

var stringBuilder = function (str) {
  this.arr = new Array();
  this.length = 0;
  if (str) {
    this.arr.push(str);
    this.length += str.length;
  }
  if (!stringBuilder.created) {
    stringBuilder.prototype.append = function (str) {
      this.arr.push(str);
      this.length += str.length;
      return this;
    };
    stringBuilder.prototype.clear = function () {
      this.arr.splice(0, this.arr.length);
      this.length = 0;
      return this;
    };
    stringBuilder.prototype.join = function (str) {
      return this.arr.join(str);
    };
    stringBuilder.created = true;
  }
}