Functions in JavaScript


In JavaScript, a function is a block of code that is defined once and can be executed multiple times. Functions are a fundamental building block of the language, and they can be used in a variety of ways.

Here are some key points about functions in JavaScript:

  • Functions are defined using the function keyword, followed by the function name, a set of parentheses, and a set of curly braces that contain the code for the function.
  • Functions can take zero or more arguments, which are values that are passed into the function when it is called. The values passed in are called “parameters.”
  • Functions can return a value using the return keyword. If a function does not return a value, it returns undefined by default.
  • Functions can be defined as part of an object (in which case they are called “methods”) or as standalone functions.
  • Functions can be stored in variables, arrays, or objects, and they can be passed as arguments to other functions.

Here is an example of a simple function that takes two arguments and returns their sum:

function add(x, y) {
  return x + y;

console.log(add(2, 3));  // outputs 5

Functions can also be defined using function expressions, which are a more concise syntax for defining functions. Here is the same function defined using a function expression:

const add = function(x, y) {
  return x + y;

console.log(add(2, 3));  // outputs 5

In modern JavaScript, you can also define functions using the “arrow function” syntax, which is even more concise than function expressions. Here is the same function defined using an arrow function:

const add = (x, y) => x + y;
console.log(add(2, 3));  // outputs 5

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