To return the response from an asynchronous call in JavaScript, it’s important to understand how JavaScript handles asynchronous operations like fetching data, reading files, or executing time-based actions. JavaScript is a single-threaded nature means it can only handle one task at a time, but it uses asynchronous programming to execute tasks without blocking the main thread.
You can manage asynchronous calls using callbacks, promises, or the async/await syntax, as well as the Promise syntax. These methods help return responses efficiently and improve the readability and maintainability of the code.
Return Response using a Callback Function
function fetchData(callback) {
setTimeout(() => {
const s = "Return Response Using a Callback Function";
callback(s);
}, 1000);
}
// Using the callback
fetchData((response) => {
console.log(response);
});Return Response using Promises
function fetchData() {
return new Promise((resolve, reject) => {
setTimeout(() => {
const s = "Return Response Using Promises";
resolve(s);
}, 1000);
});
}
// Using the promise
fetchData()
.then((response) => {
console.log(response);
})
.catch((error) => {
console.error("Error:", error);
});Return Response using Async/Await
async function fetchData() {
return new Promise((resolve, reject) => {
setTimeout(() => {
const a = "Return Response Using Async/Await";
resolve(a);
}, 1000);
});
}
async function getData() {
try {
// Waits for the promise to resolve
const response = await fetchData();
console.log(response);
} catch (error) {
console.error("Error:", error);
}
}
getData();