js日期 操作

//重写toString方法，将时间转换为Y-m-d H:i:s格式
Date.prototype.toString = function(){
    return this.getFullYear() + "-" + (this.getMonth()+) + "-" + this.getDate() + " " + this.getHours() + ":" + this.getMinutes() + ":" + this.getSeconds();
}
//格式化时间字符串
Date.prototype.toFormatString = function(format){
    if(format == ""){
        return this.toString();
    }
    var str = '';
    str = format.replace(/Y|y/,this.getFullYear())
                .replace(/M|m/,this.getMonth() + )
                .replace(/D|d/,this.getDate())
                .replace(/H|h/,this.getHours())
                .replace(/I|i/,this.getMinutes())
                .replace(/S|s/,this.getSeconds());
    return str;
}
//在当前时间上添加年数
Date.prototype.addYear = function(years){
    var cyear = this.getFullYear();
    cyear += years;
    this.setYear(cyear);
    return this;
}
//在当前时间上添加天数
Date.prototype.addDay = function(days){
    var cd = this.getDate();
    cd += days;
    this.setDate(cd);
    return this;
}
//在当前时间上添加月数
Date.prototype.addMonth = function(months){
    var cm = this.getMonth();
    cm += months;
    this.setMonth(cm);
    return this;
}