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<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>promise.all</title>
</head>
<body>
<script>
let link = `https://github.com/shfshanyue/Daily-Question/issues/500`;
function pAll(_promises) {
return new Promise((resolve, reject) => {
// Iterable => Array
const promises = Array.from(_promises);
// 结果用一个数组维护
const r = [];
const len = promises.length;
let count = 0;
for (let i = 0; i < len; i++) {
// Promise.resolve 确保把所有数据都转化为 Promise
Promise.resolve(promises[i])
.then(o => {
// 因为 promise 是异步的，保持数组一一对应
r[i] = o;
// 如果数组中所有 promise 都完成，则返回结果数组
if (++count === len) {
resolve(r);
}
// 当发生异常时，直接 reject
})
.catch(e => reject(e));
}
});
}
</script>
<script>
const sleep = seconds => new Promise(resolve => setTimeout(() => resolve(seconds), seconds));
</script>
<script>
function promiseAll(_promises) {
return new Promise((resolve, reject) => {
const promises = [..._promises];
const arr = [];
let count = 1;
for (let i = 0; i < promises.length; i++) {
Promise.resolve(promises[i]).then(
data => {
arr[i] = data;
if (++count === promises.length) {
resolve(arr);
}
},
err => {
reject(err);
}
);
}
});
}
</script>
<script>
function makeIterator(array) {
let nextIndex = 0;
return {
next: function () {
return nextIndex < array.length
? {
value: array[nextIndex++],
done: false
}
: {
done: true
};
}
};
}
let it = makeIterator(['哟', '呀']);
console.log(it.next().value); // '哟'
console.log(it.next().value); // '呀'
console.log(it.next().done); // true
</script>
</body>
</html>
