In JavaScript, asynchronous code can be accomplished using async/await, Promises and callbacks.

Async/Await:

Async/await is a new feature in ES2017 that allows us to write asynchronous code that looks and behaves like synchronous code. It is built on top of Promises and makes the code more readable and easier to reason about.

Here's an example of async/await in JavaScript:

index.tsx
async function getData() {
  const response = await fetch('https://jsonplaceholder.typicode.com/todos/1');
  const data = await response.json();
  console.log(data);
}

getData();
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Promises:

Promises are the most widely used way to do asynchronous programming in JavaScript. Promises represent a value that may not yet be available, but will be at some point in the future. They allow us to write asynchronous code that is more readable and easier to understand.

Here's an example of Promises in JavaScript:

index.tsx
fetch('https://jsonplaceholder.typicode.com/todos/1')
  .then(response => response.json())
  .then(data => console.log(data))
  .catch(err => console.error(err));
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Callbacks:

Callbacks are the oldest and most basic way to do asynchronous programming in JavaScript. Callbacks are functions that are passed as arguments to other functions and are called once the asynchronous operation is complete.

Here's an example of Callbacks in JavaScript:

index.tsx
function getData(callback) {
  fetch('https://jsonplaceholder.typicode.com/todos/1')
    .then(response => response.json())
    .then(data => callback(data))
    .catch(err => console.error(err));
}

getData(data => console.log(data));
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In conclusion, async/await, Promises, and callbacks are all viable options for handling asynchronous code in JavaScript. It's important to choose the one that fits your particular use case the best.