日期时间转换方法

1.获取的时间转换为想要的日期时间格式：

function getTimetrans(){
    const date = new Date();//如果date为13位不需要乘1000
    const Y = date.getFullYear() + '-';
    const M = (date.getMonth()+1 < 10 ? '0'+(date.getMonth()+1) : date.getMonth()+1) + '-';
    const D = (date.getDate() < 10 ? '0' + (date.getDate()) : date.getDate()) + ' ';
    const h = (date.getHours() < 10 ? '0' + date.getHours() : date.getHours()) + ':';
    const m = (date.getMinutes() <10 ? '0' + date.getMinutes() : date.getMinutes()) + ':';
    const s = (date.getSeconds() <10 ? '0' + date.getSeconds() : date.getSeconds());
    return Y+M+D+h+m+s;
}

2.获取的时间转换为星期格式：

function getWeekDate(){
    const date = new Date();//如果date为13位不需要乘1000
    const day = date.getDay();
    const weeks = ["星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"];
    const week = weeks[day];
    return week;
}

3.时间转换为毫秒：

　　1）方法一：　getTime()/Date.parse()

const oldTime = (new Date("2020/08/14 15:00:00")).getTime(); //得到毫秒数 

//注：日期格式是:yyyy-mm-dd hh:mm:ss需要转化格式

let startDate ='2020-08-14 15:00:00';
     startDate= startDate.replace(new RegExp("-","gm"),"/");
let startDateM = (new Date(startDate)).getTime(); //得到毫秒数

//或者
let str = '2020-08-14 15:00:00';

let arr = str.split(/[- : /]/);
let startDate = Date.parse(new Date(arr[0], arr[1]-1, arr[2], arr[3], arr[4], arr[5]));
console.log(startDate)//1597388400000

　　2）方法=：valueOf()

let dateTime = '2020-08-14 15:00:00';
console.log(dateTime.valueOf());//2020-08-14 15:00:00

let dateTime1 = new Date();
console.log(dateTime1.valueOf());//1597389982770

let dateTime2 = new Date('2020-08-14 15:00:00');
console.log(dateTime2.valueOf());//1597388400000

let timeVale = Date.parse('2020-08-14 15:00:00');//APP中直接使用此方法会报错
console.log(timeVale);//1597388400000

　import moment from 'moment';//react-native项目安装的插件

let timeVale2 = moment('2020-08-14 15:00:00').valueOf();//转换为毫秒(APP中使用不会报错)
console.log(timeVale2);//1597388400000