获取本月的第一天和最后一天

var firstDate = new Date();
firstDate.setDate(1); //第一天
var endDate = new Date(firstDate);
endDate.setMonth(firstDate.getMonth()+1);
endDate.setDate(0); alert("第一天："+firstDate.format('yyyy-MM-dd 00:00:00')+" 最后一天："+endDate.format('yyyy-MM-dd 23:59:59'));

//时间格式化
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;
}