JS字符串函数扩展代码

/**************************************************** 
*CreateBy:joe zhou 
*CreateDate:2011-9-4 
*Description:字符串辅助函数 
****************************************************/ 
//String.prototype = { 
// caption: function () { 
// }, 
// leftPad: function (padChar, width) { 
// if (this.length >= width) { 
// return this; 
// } 
// } 
//}; 
String.prototype.padLeft = function (padChar, width) { 
var ret = this; 
while (ret.length < width) { 
if (ret.length + padChar.length < width) { 
ret = padChar + ret; 
} 
else { 
ret = padChar.substring(0, width-ret.length) + ret; 
} 
} 
return ret; 
}; 
String.prototype.padRight = function (padChar, width) { 
var ret = this; 
while (ret.length < width) { 
if (ret.length + padChar.length < width) { 
ret += padChar; 
} 
else { 
ret += padChar.substring(0, width - ret.length); 
} 
} 
return ret; 
}; 
String.prototype.trim = function () { 
return this.replace(/^\s+/, '').replace(/\s+$/, ''); 
}; 
String.prototype.trimLeft = function () { 
return this.replace(/^\s+/, ''); 
}; 
String.prototype.trimRight = function () { 
return this.replace(/\s+$/, ''); 
}; 
String.prototype.caption = function () { 
if (this) { 
return this.charAt(0).toUpperCase() + this.substr(1); 
} 
return this; 
}; 
String.prototype.reverse = function () { 
var ret = ''; 
for (var i = this.length - 1; i >= 0; i--) { 
ret += this.charAt(i); 
} 
return ret; 
}; 
String.prototype.startWith = function (compareValue, ignoreCase) { 
if (ignoreCase) { 
return this.toLowerCase().indexOf(compareValue.toLowerCase()) == 0; 
} 
return this.indexOf(compareValue) == 0 
}; 
String.prototype.endWith = function (compareValue, ignoreCase) { 
if (ignoreCase) { 
return this.toLowerCase().lastIndexOf(compareValue.toLowerCase()) == this.length - compareValue.length; 
} 
return this.lastIndexOf(compareValue) == this.length - compareValue.length; 
};