Search⌘ K
AI Features
Home
Courses
Using fp-ts for Functional Programming in TypeScript

Creating Functions in JavaScript

Explore how to create functions in JavaScript using the function keyword, closures, and arrow functions. Understand how closures enable private variables and function factories, and learn stylistic improvements with implicit returns and nested functions for cleaner, maintainable code.

We'll cover the following...

There are many ways to create functions in JavaScript. Let’s see what they are.

The function keyword

The whole function consists of the following parts.

The basic syntax to create a function in JavaScript is using the function keyword. Let’s look at an example below.

C++
function example() {
    console.log('Print a message');
}
example();

We’ve created a simple function using the function keyword in the code snippet above. It logs Print a message to the console.

Creating function within a function

Since functions are first-class citizens in JavaScript, we can also do things like creating a function that itself creates functions. Let’s look at an example below.

C++
function withInnerFunction(outer) {
    return function ourInnerFunction(inner) {
        console.log(`Outer function received ${outer}, inner got ${inner}`);
    };
}
const returnedFunction = withInnerFunction('a');
// some time later in our program, we actually need to call returnedFunction 
returnedFunction('b');

In the code ...