实现日期格式化函数、实现数组元素求和

1 实现日期格式化函数

function dateFormat(date, format) {
    let year = date.getFullYear();
    let month = date.getMonth() + 1;
    let day = date.getDate();
    format = format.replace(/yyyy/, year);
    format = format.replace(/MM/, month < 10 ? `0${month}` : month);
    format = format.replace(/dd/, day < 10 ? `0${day}` : day);
    return format;
}

console.log(dateFormat(new Date('2024-12-31'), 'yyyy/MM/dd')); // 2024/12/31
console.log(dateFormat(new Date('2025-02-08'), 'yyyy/MM/dd')); // 2025/05/08
console.log(dateFormat(new Date('2025-02-08'), 'yyyy年MM月dd日')); // 2025年02月08日

2 实现数组元素求和

arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

function add(arr) {
    let sum = arr.reduce((total, item) => {
        return total += item;
    }, 0);
    return sum;
}
console.log(add(arr)); //55

arr = [1, 2, 3, [[4, 5], 6], 7, 8, 9];

function add(arr) {
    let sum = arr.toString().split(',').reduce((total, item) => {
        return total += Number(item);
    }, 0);
    return sum;
}
console.log(add(arr)); //45