The Difference Between Function Expression and Function Declaration in JavaScript

Function expressions and declarations have two major differences. One is that for function expressions, you are assigning the function to a variable. In a function declaration, you don't:

// Function expression
// Will throw a TypeError
console.log(func());
var func = function() { return 5; }

// Function declaration
// Will run without a problem, because it is hoisted
console.log(func());
function func() { return 5; }

The biggest difference however is that expressions are not hoisted. If you call the function before it was initialized, you will get a type error:

Whichever you choose to use throughout your code, make sure you stay consistent to avoid unexpected behaviors.

50 JavaScript Interview QuestionsAnd their answers explainedHere are 50 JavaScript interview questions that often come up during a technical interview. In one place, one resource to learn from.Learn More

Get access to 300+ webtips 💌

Level up your skills and master the art of frontend development with bite-sized tutorials.

We don't spam. Unsubscribe anytime.

Get Access to Webtips

Looking to improve your skills? Check out our interactive course to master JavaScript from start to finish.

---

Resources:

• Function expression
• Function declaration