Async-Await

Async Await

Sources

• JS Info
• James Q Quick's Video

An evolution on Promises is the await and async syntax. These allwo you to write and consume process a little easier than using the base syntax.

Now instead of writing out the promises like referenced in the promises note we can write the following:

import fetch from 'node-fetch';

const fetchPokes = async (id) => {
  try {
    const res = await fetch(`https://pokeapi.co/api/v2/pokemon/${id}`);
    const data = await res.json();
    console.log(data);
  } catch (err) {
    console.error(err);
  }
};

fetchPokes(1);

In the above example, we're prepending the function signature with the keyword async, adding in the await keyword at the front of the variable assignment, and then wrapping those in a try/catch statement.

Async

Async is a special keyword in JS which you put before the function. This will make the function always return a promise object. Anything in that block is also wrapped in a resolved promise automatically.

Await

Await is only valid inside an async function. This keyword makes JS wait until that promise finishes and returns the result.

The function execution pauses on the line with an await. It only restarts when the result object comes back. This does not cost CPU cycles as JS can do other things while this waits for the response back.

Await can only be used in an async function and will throw and error if applied anywhere else.

#JavaScript