JavaScript_code_snippets/promise_practice.html at master · dendoink/JavaScript_code_snippets · GitHub

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<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>promise_practice</title>
</head>

<body>
    <div class="container">
        <div id="signal"></div>
    </div>
</body>
<script>
    // promise 练习demo
    // 红绿灯，红灯3秒，绿灯10秒，黄灯2秒
    // let signal = document.getElementById('signal')
    // function red_3() {
    //     signal.setAttribute('class', 'red')
    //     setTimeout(() => {
    //         yellow_2()
    //     }, 3000)
    // }
    // function yellow_2() {
    //     signal.setAttribute('class', 'yellow')
    //     setTimeout(() => {
    //         green_10()
    //     }, 2000)
    // }
    // function green_10() {
    //     signal.setAttribute('class', 'green')
    //     setTimeout(() => {
    //         red_3()
    //     }, 5000)
    // }
    // red_3()

    function wait(time) {
        return new Promise((resolve, reject) => {
            setTimeout(resolve, time * 1000);
        })
    }

    async function changeColor(time, color) {
        signal.setAttribute('class', color)
        await wait(time)
    }

    async function main() {
        while (true) {
            await changeColor(2, 'red')
            await changeColor(3, 'yellow')
            await changeColor(5, 'green')
        }
    }
    main()
</script>
<style>
    .container {
        width: 100%;
        height: 100vh;
        display: flex;
        justify-content: center;
        align-items: center
    }

    #signal {
        width: 100px;
        height: 100px;
        border-radius: 50%;
    }

    .green {
        background: green;
    }

    .red {
        background: red;
    }

    .yellow {
        background: yellow;
    }
</style>

</html>