date 日期格式化--YYYY-MM-DD

Date.prototype.format = function (format) {
    var o = {
        "M+": this.getMonth() + 1, //month
        "d+": this.getDate(),    //day
        "h+": this.getHours(),   //hour
        "m+": this.getMinutes(), //minute
        "s+": this.getSeconds(), //second
        "q+": Math.floor((this.getMonth() + 3) / 3),  //quarter
        "S": this.getMilliseconds() //millisecond
    }
    if (/(y+)/.test(format)) format = format.replace(RegExp.$1,(this.getFullYear() + "").substr(4 - RegExp.$1.length));
    for (var k in o)
     if (new RegExp("(" + k + ")").test(format))
        format = format.replace(RegExp.$1, RegExp.$1.length == 1 ? o[k] :("00" + o[k]).substr(("" + o[k]).length));
    return format;
}

    var _start = new Date();
    var _strTime = _start.format('yyyy-MM-dd')