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;
}