LANGUAGE » JAVASCRIPT
Function
Basic
Declaraction:
js
function sum(a, b) {
return a + b;
}
Calling the function:
js
const result = sum(8, 16);
Async
Declaration
Async functions are functions that return a Promise
:
js
function getUser() {
return new Promise((resolve, reject) => {
resolve({ id: 1 });
});
}
The async
keyword can also be used if using modules:
js
async function getUser() {
return { id: 1 };
}
Calling async functions
Calling it and getting the result:
js
// Using callback
getUser().then((user) => {});
// Using await
const user = await getUser();
Wait all
First put all promises in an array:
ts
const promises: Promise<any>[] = [];
promises.push(fetch('example.com/1'));
promises.push(fetch('example.com/2'));
promises.push(fetch('example.com/3'));
Use this if the result of all promises are needed.
ts
Promise.allSettled(promises).then((results) => {
results.forEach((result) => {
if (result.status === 'fulfilled') {
response = result.value;
} else {
error = result.reason;
}
});
});
Or this to stop as soon an any promise fails.
ts
Promise.all(promises).then((responses) => {
// All promises resolved
}).catch((error) => {
// First failed promise
});