node.js async/await 继发执行与并发执行

电玩女神 2022-01-17 01:11 329阅读 0赞

async/await 继发执行与并发执行，看如何控制

两个异步函数 foo bar

function foo() {
        return new Promise((resolve, reject) => {
            setTimeout(() => {
                console.log('foo:' + new Date().toLocaleString())
                resolve('foo')
            }, 2000)
        })
    }
    
    function bar() {
        return new Promise((resolve, reject) => {
            setTimeout(() => {
                console.log('bar:' + new Date().toLocaleString())
                resolve('bar')
            }, 2000)
        })
    }

继发执行

//继发执行
    async function main() {
        console.log('beginTime:' + new Date().toLocaleString())
        var foostr = await foo();
        console.log(new Date().toLocaleString())
        console.log(foostr);
        var barstr = await bar();
        console.log(new Date().toLocaleString())
        console.log(barstr);
        console.log('endTime:' + new Date().toLocaleString())
    }
    
    //继发执行
    async function main2() {
        let docs = [foo, bar];
        console.log('beginTime:' + new Date().toLocaleString())
        for (let doc of docs) {
            var str = await doc();
            console.log(new Date().toLocaleString())
            console.log(str);
        }
        console.log('endTime:' + new Date().toLocaleString())
    }

并发执行

//并发执行 
    async function async_main() {
        console.log('beginTime:' + new Date().toLocaleString())
        let [get_foo, get_bar] = await Promise.all([foo(), bar()]);
        console.log(new Date().toLocaleString());
        console.log(get_foo);
        console.log(get_bar);
        console.log('endTime:' + new Date().toLocaleString())
    }
    
    
    //并发执行 
    async function async_main4() {
        let docs = [foo(), bar()];
        console.log('beginTime:' + new Date().toLocaleString())
        for (let doc of docs) {
            var str = await doc;
            console.log(new Date().toLocaleString())
            console.log(str);
        }
        console.log('endTime:' + new Date().toLocaleString())
    
    }
    
    
    //并发执行
    async function async_main2() {
        console.log('beginTime:' + new Date().toLocaleString())
        let fooPromise = foo();
        let barPromise = bar();
        let get_foo = await fooPromise;
        console.log(new Date().toLocaleString());
        console.log(get_foo);
        let get_bar = await barPromise;
        console.log(new Date().toLocaleString());
        console.log(get_bar);
        console.log('endTime:' + new Date().toLocaleString())
    }