How to Ensure Function Completion in JavaScript: Callbacks, Arrow Functions, and Async/Await?

Waiting for Function Completion in JavaScript

In JavaScript, where many operations are asynchronous, there may be instances where you need to ensure that one function finishes before proceeding with another.

Callback Functions

One common approach is to utilize callback functions. The calling function passes a callback as an argument to the function it invokes. When the called function completes its asynchronous task, it executes the callback, allowing the calling function to continue its execution.

For instance:

<code class="js">function firstFunction(_callback) {
  // Perform asynchronous work here...
  // Invoke the callback when finished
  _callback();
}

function secondFunction() {
  // Call first function with a callback
  firstFunction(function() {
    console.log('First function completed.');
  });
}</code>

Arrow Functions

Arrow functions provide a more concise syntax for callback functions:

<code class="js">firstFunction(() => console.log('First function completed.'));</code>

Alternatives: Async/Await

For clarity and maintainability, modern JavaScript introduces async/await. This allows you to write your code in a pseudo-synchronous style, even when dealing with asynchronous operations:

<code class="js">const secondFunction = async () => {
  const result = await firstFunction();
  // Continue execution after first function completes
};</code>

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