• Functions
• Last updated on January 14, 2018

Writing a Function

Functions are blocks of code that can be used to run a task. Let’s look at how we can use them to make our code easier to write and maintain.

There have historically been two ways to write a function.

// Function declaration
function add (num1, num2) {
	return num1 + num2;
}

// Function expression
let add = function (num1, num2) {
	return num1 + num2;
};

The first example, function add () {}, is called a function declaration. The second example, let add = function () {}, is called a function expression.

They more-or-less do the same thing, but there’s one subtle yet important difference between them.

Note: There’s now a third way—ES6 arrow functions—that we’ll talk about in a later chapter.

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