CODEWITHSUNDEEP
javascriptgoogle-chrome-extensionasync-awaitecmascript-2017
Drew
Drew

Reputation: 710

JavaScript await by default instead of manually

Async/await are really handy, but I want the opposite of their behavior. Instead of other functions continuing on unless I manually ask them to await a promise, I want functions to yield unless I manually specify that they continue running in parallel.

For instance, this code would print out 1 3 2:

function wait(ms) {
    return new Promise(r => setTimeout(r, ms));
}

async function a() {
    console.log("1");
    await wait(5000);
    console.log("2");
}

a();
console.log("3");

I want it to print out 1 2 3, with function a() not actually returning until I've waited 5 seconds and 2 has been printed. I'm making an extension that I'd prefer to be lightweight, so I'd rather not use 3rd party libraries.

Is there any way to do this?

Upvotes: 3

Views: 1181

Answers (1)

jib
jib

Reputation: 42500

Implicit await is bad, for reasons covered well in this blog. In short, consider why there's no need for locking in JavaScript. It's because we don't worry about being pre-empted willy-nilly.

Also, as mentioned by Daniel in comments, global await is not allowed either, presumably for backwards compatibility.

You can work around this by wrapping your top-level code like this: 

let wait = ms => new Promise(r => setTimeout(r, ms));

async function a() {
  console.log("1");
  await wait(5000);
  console.log("2");
}

(async () => {

  // Put your top level code here!

  await a();
  console.log("3");

})().catch(e => setTimeout(() => { throw e; }));

Not perfect, but gets the job done, without turning everything upside down.

Upvotes: 3

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