一些工具函数

// 1、睡眠函数
function sleep(time) {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve();
        }, time)
    })
}
// 使用
async function main() {
    console.log(1);
    await sleep(2000);
    console.log(2); // 两秒之后输出 2
}


// 2、事件循环面试题
async function async1() {
    console.log('async1 start');
    await async2();
    console.log('async1 end');
}
    
async function async2() {
    new Promise((resolve) => {
        console.log('new promise');
        resolve();
    }).then(() => {
        console.log('async2 end');
    })
}
    
setTimeout(() => {
    console.log('settimeout');
},0)

console.log('script start');

async1();
    
new Promise((resolve) => {
    console.log('promise2');
    resolve();
}).then(() => {
    console.log('pormise4')
})
    
console.log('script end');
// 3、 useMemo 和 useCallback