handwriting-algorithm/22promiseAll.html at master · ustcfury/handwriting-algorithm · GitHub

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

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

<body>
    <script>
        function promiseAll(promises) {
            return new Promise(function (resolve, reject) {
                if (!Array.isArray(promises)) {
                    throw new TypeError(`argument must be a array`)
                }
                var resolvedCounter = 0;
                var promiseNum = promises.length;
                var resolvedResult = [];
                for (let i = 0; i < promiseNum; i++) {
                    promises[i].then(value => {
                        resolvedCounter++;
                        resolvedResult[i] = value;
                        if (resolvedCounter == promiseNum) {
                             resolve(resolvedResult)
                        }
                    }, error => {
                         reject(error)
                    })
                }
            })
        }
        // test
        let p1 = new Promise(function (resolve, reject) {
            setTimeout(function () {
                resolve(1)
            }, 1000)
        })
        let p2 = new Promise(function (resolve, reject) {
            setTimeout(function () {
                resolve(2)
            }, 2000)
        })
        let p3 = new Promise(function (resolve, reject) {
            setTimeout(function () {
                resolve(3)
            }, 3000)
        })
        promiseAll([p3, p1, p2]).then(res => {
            console.log(res) // [3, 1, 2]
        })
    </script>
</body>

</html>