Await halts the execution of our async function. This allows us to conveniently write synchronous-style code to handle dependent promises. But what if our async function contains multiple promises which are not dependent on the results of one another to execute?
async function waiting() {
const firstValue = await firstAsyncThing();
const secondValue = await secondAsyncThing();
console.log(firstValue, secondValue);
}
async function concurrent() {
const firstPromise = firstAsyncThing();
const secondPromise = secondAsyncThing();
console.log(await firstPromise, await secondPromise);
}In the waiting() function, we pause our function until the first promise resolves, then we construct the second promise. Once that resolves, we print both resolved values to the console.
In our concurrent() function, both promises are constructed without using await. We then await each of their resolutions to print them to the console.
With our concurrent() function both promises’ asynchronous operations can be run simultaneously. If possible, we want to get started on each asynchronous operation as soon as possible.
Within our async functions we should still take advantage of concurrency, the ability to perform asynchronous actions at the same time.
Note: if we have multiple truly independent promises that we would like to execute fully in parallel, we must use individual .then() functions and avoid halting our execution with await.
