语法
js
next()
next(value)
参数
value可选-
一个可选值，用于修改生成器的内部状态。传递给
next()方法的值将由yield接收。
返回值
示例
使用 next()
以下示例展示了一个生成器以及 next 方法返回的对象。
js
// An async task. Pretend it's doing something more useful
// in practice.
function delayedValue(time, value) {
return new Promise((resolve, reject) => {
setTimeout(() => resolve(value), time);
});
}
async function* createAsyncGenerator() {
yield delayedValue(500, 1);
yield delayedValue(500, 2);
yield delayedValue(500, 3);
}
const asyncGen = createAsyncGenerator();
asyncGen.next().then((res) => console.log(res)); // { value: 1, done: false }
asyncGen.next().then((res) => console.log(res)); // { value: 2, done: false }
asyncGen.next().then((res) => console.log(res)); // { value: 3, done: false }
asyncGen.next().then((res) => console.log(res)); // { value: undefined, done: true }
向生成器发送值
在此示例中，next 是带值调用的。
注意： 第一次调用不会输出任何内容，因为生成器最初没有产生任何值。
js
// An async task. Pretend it's doing something more useful
// in practice.
function sleep(time) {
return new Promise((resolve, reject) => {
setTimeout(resolve, time);
});
}
async function* createAsyncGenerator() {
while (true) {
await sleep(500);
const value = yield;
console.log(value);
}
}
async function main() {
const asyncGen = createAsyncGenerator();
// No log at this step: the first value sent through `next` is lost
console.log(await asyncGen.next(1)); // { value: undefined, done: false }
// Logs 2: the value sent through `next`
console.log(await asyncGen.next(2)); // { value: undefined, done: false }
}
main();
规范
| 规范 |
|---|
| ECMAScript® 2026 语言规范 # sec-asyncgenerator-prototype-next |
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