handwriting-algorithm/29promiseAllSettled.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>
        Promise.allSettled = function (promises) {
            return new Promise(resolve => {
                const data = [], len = promises.length;
                let count = len;
                for (let i = 0; i < len; i += 1) {
                    const promise = promises[i];
                    promise.then(value => {
                        data[i] = { status: 'fulfilled', value };
                    }, error => {
                        data[i] = { status: 'rejected', error };
                    }).finally(() => { // promise has been settled
                        if (!--count) {
                            resolve(data);
                        }
                    });
                }
            });
        }
        let p1 = new Promise(function (resolve, reject) {
            setTimeout(function () {
                resolve(1)
            }, 1000)
        })
        let p2 = new Promise(function (resolve, reject) {
            setTimeout(function () {
                reject(2)
            }, 2000)
        })
        let p3 = new Promise(function (resolve, reject) {
            setTimeout(function () {
                resolve(3)
            }, 3000)
        })
        Promise.allSettled([p3, p1, p2]).then(res => {
            console.log(res) // [3, 1, 2]
        })
    </script>
</body>

</html>