封装当前星期几的函数

法1 if - else if - else 语句

let date = new Date()
let day = date.getDay()

function fnDay(num){
    if(num===0){
        return '星期天'
    }else if(num===1) {
        return '星期一'
    }else if(num===2) {
        return '星期二'
    }else if(num===3) {
        return '星期三'
    }else if(num===4) {
        return '星期四'
    }else if(num===5) {
        return '星期五'
    }else {
        return '星期六'
    }
}

console.log(fnDay(day))

法2 switch-case 语句

let date = new Date()
let day = date.getDay()

function fnDay(num) {
    switch (num) {
        case 0:
            day = '星期天'
            break
        case 1:
            day = '星期一'
            break
        case 2:
            day = '星期二'
            break
        case 3:
            day = '星期三'
            break
        case 4:
            day = '星期四'
            break
        case 5:
            day = '星期五'
            break
        case 6:
            day = '星期六'
            break
    }
    return day
}

console.log(fnDay(day))

法3 巧用数组下标

let date = new Date()
let day = date.getDay()

function fnDay(num){
    let arr =['星期天','星期一','星期二','星期三','星期四','星期五','星期六']
    return arr[num]
}

console.log(fnDay(day))