I've got the following code block:
new Promise((res, rej) => {
if (checkCondition()) {
res(getValue())
} else {
getValueAsync((result) => {
res(result)
})
}
}).then((value) => {
doStuff(value)
})
I'd like to convert this to use async/await, but I can't figure out how to do it. I know when you're working exclusively with promises, you replace the calls to then() with value = await ..., but How do I make this work with callbacks? Is it possible?
First of all, you have to make sure you are in an async function to begin with. Then it could be something along the lines of:
async function example() {
let value = (checkCondition() ? getValue() : await getValueAsync());
doStuff(value);
}
await example();
This, however, assumes that you can modify getValueAsync as well, to make it an async function or to make it return a Promise. Assuming getValueAsync has to take a callback, there is not that much we can do:
async function example() {
let value = (checkCondition()
? getValue()
: await new Promise(res => getValueAsync(res))
);
doStuff(value);
}
await example();
You still gain the benefit of not having to create the full Promise chain yourself. But, getValueAsync needs to be wrapped in a Promise in order to be usable with await. You should carefully consider whether this kind of a change is worth it for you. E.g. if you are in control of most of the codebase and / or most of the functions you are calling are already async / return Promises.
