js异步小笔记-CFANZ编程社区

js异步小笔记
<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
    </head>
    <body>
        <button id="btn" onclick="handle()">点击</button>
    </body>
    <script type="text/javascript">
        function fn1(){
            return new Promise((resolve,reject) =>{
                setTimeout(() =>{
                    resolve(1)
                },1000)
            })
        }
        function fn2(){
            return new Promise((resolve,reject) =>{
                setTimeout(() =>{
                    resolve(2)
                },3000)
            })

        }
        //这里的结果就是先打印2，再打印1
        async function handle(){
            let a  = await fn2()
            console.log(a)
            let b = await fn1()
            console.log(b)
        }



        function fn3(){
            setTimeout(() =>{
                    console.log(3)
                },1000)
        }
        function fn4(){
            setTimeout(() =>{
                    console.log(4)
                },3000)
        }
        //这里的结果就是先打印3，再打印4
        function handle(){
            fn4()
            fn3()
        }
    </script>
</html>
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