参考答案

String.prototype.trim = function(mode)
{//前后去空格
        if (mode==’left’) {
                return ((this.charAt(0) == ” “ && this.length > 0) ? this.slice(1).trim(’left’) : this);
        } else
                if (mode == ’right’) {
                        return ((this.charAt(this.length - 1) == ” “ && this.length > 0) ? this.slice(0, this.length - 1).trim(’right’) : this);
                } else {
                        return this.trim(’left’).trim(’right’);
        }
};