[英]How to have an async endless loop with Promises
I need to have an "endless" while-loop which has promises inside it.我需要一个“无休止的”while 循环,里面有承诺。 Here's some example code:
下面是一些示例代码:
let noErrorsOccured = true
while (noErrorsOccured){
someAsyncFunction().then(() => {
doSomething();
}).catch((error) => {
console.log("Error: " + error);
noErrorsOccured = false;
});
}
function someAsyncFunction() {
return new Promise ((resolve, reject) => {
setTimeout(() => {
const exampleBool = doSomeCheckup();
if (exampleBool){
resolve();
} else {
reject("Checkup failed");
}
}, 3000);
});
}
So this while-loop should run endless, except an error occurs, then the while-loop should stop.所以这个while循环应该无休止地运行,除非发生错误,然后while循环应该停止。 How can I achieve this?
我怎样才能做到这一点?
I hope you can understand what I mean and thanks in advance.我希望你能理解我的意思,并提前致谢。
How can I achieve this?
我怎样才能做到这一点?
Not with a blocking loop since promises won't be able to settle.没有阻塞循环,因为承诺将无法解决。 You can learn more about JavaScript's event loop on MDN .
您可以在 MDN 上了解有关JavaScript 事件循环的更多信息。
Instead, call the function again when the promise is resolved:相反,当 promise 被解析时再次调用该函数:
Promise.resolve().then(function resolver() {
return someAsyncFunction()
.then(doSomething)
.then(resolver);
}).catch((error) => {
console.log("Error: " + error);
});
This is what worked for me (based on discussion here: https://github.com/nodejs/node/issues/6673 ) in NodeJS:这对我有用(基于这里的讨论: https : //github.com/nodejs/node/issues/6673 )在 NodeJS 中:
async function run(){
// Do some asynchronous stuff here, e.g.
await new Promise(resolve => setTimeout(resolve, 1000));
}
(function loop(){
Promise.resolve()
.then(async () => await run())
.catch(e => console.error(e))
.then(process.nextTick(loop));
})();
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