This content originally appeared on DEV Community and was authored by DEV Community
Sometimes you want your synchronous function to run asynchronously. Perhaps you want to run multiple functions asynchronously using something like Promise.allSettled or Promise.all.
I have a number of setup functions that dont depend on each other in an application and I was curious how hard it would be to convert the setup functions to async functions without touching their internal code. (Some functions come from libraries)
The TLDR is that yes, I managed to do it.
function asPromise (callback, ...args) {
return new Promise((resolve, reject) => {
try {
resolve(callback(...args))
} catch(e) {
reject(e)
}
})
}
Now for some examples:
function greet (greeting, name) { return "${greeting}, {name}" }
await asPromise(greet, "hi", "konnor")
// => "hi, konnor"
Now what if we pass an object?
function greet ({greeting, name}) { return "${greeting}, {name}" }
await asPromise(greet, {greeting: "hi", name: "konnor"})
// => "hi, konnor"
And finally, what about an array?
function greet (ary) {
return `${ary[0]}, ${ary[1]}`
}
await asPromise(greet, ["hi", "konnor"])
// => "hi, konnor"
Are there edge cases? Probably. Mostly around this
if your function calls rely on this make sure to bind within the Promise like so:
await asPromise(myFunction.bind(myThis), "arg1")
And that's all for today! Short and sweet.
This content originally appeared on DEV Community and was authored by DEV Community
DEV Community | Sciencx (2022-03-13T01:45:42+00:00) Converting a callback to a promise. Retrieved from https://www.scien.cx/2022/03/13/converting-a-callback-to-a-promise/
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