日期格式化（包括日期对象和字符串）

dateObj = {
reg: /^[0-9]{4}[-|/](0?[1-9]|1[0-2])[-|/]((0?[1-9])|((1|2)[0-9])|30|31)$/,
formatDate: function(dates, symbol, cpt) {
//dates:日期，可以是日期对象（new Date()），可以是字符串"2017-05-20"
//symbol:年月日之间的分割符
//cpt：月和日小于9时是否自动补零
var that = this;
if (symbol === undefined) {
symbol = "/"
}
if (cpt === undefined) {
cpt = true
}
if (dates instanceof Date) {
var year = dates.getFullYear(),
month = dates.getMonth() + 1,
day = dates.getDate() if (cpt) {
month = month < 10 ? "0" + month : month;
day = day < 10 ? "0" + day : day
}
return year + symbol + month + symbol + day
} else if (typeof dates == "string" && that.reg.test(dates)) {
var oldsymbol = dates[4];
var arr = dates.split(oldsymbol);
var year = Number(arr[0]),
month = Number(arr[1]),
day = Number(arr[2]);
if (cpt) {
month = month < 10 ? "0" + month : month;
day = day < 10 ? "0" + day : day
}
return year + symbol + month + symbol + day
} else {
return ""
}
},
splitDate: function(dates) {
var that = this;
if (typeof dates == "string" && that.reg.test(dates)) {
var oldsymbol = dates[4];
var arr = dates.split(oldsymbol);
return arr
} else {
console.warn("the string is not a dateString");
return []
}
}
}