JavaScript实现的字符串replaceAll函数代码分享

String.prototype.replaceAll = function(reallyDo, replaceWith, ignoreCase) {  
    if (!RegExp.prototype.isPrototypeOf(reallyDo)) {  
        return this.replace(new RegExp(reallyDo, (ignoreCase ? "gi": "g")), replaceWith);  
     } else {  
        return this.replace(reallyDo, replaceWith);  
     }  
}