What is function expression?

Q: What is function expression?

**function keyword:** The function keyword can be used to define a function inside an expression. A function expression is very similar to and has almost the same syntax as, a function declaration. **Can be Anonymous or Named:** The main difference between a function expression and a function declaration is the function name, which can be omitted in function expressions to create anonymous functions. **Hoisting:** You cannot call a function expression before you define it. The variable is hoisted, but the function value is not assigned until the code runs. const getRectArea = function (width, height) { return width * height; }; const countdown = function tracker(count) { if (count <= 0) { console.log("Blast off!"); return; } console.log(count); // We use 'tracker' to call the function recursively tracker(count - 1); }; countdown(3); // Attempting to call 'tracker' out here will fail // tracker(3); // ReferenceError: tracker is not defined

Difficulty: 5/10

function expressions, hoisting, IIFE

A Function Expression is when you create a function and assign it to a variable. Unlike a Function Declaration, the function is treated as a value (like a string or a number) rather than a standalone statement.

1
function keyword: The function keyword can be used to define a function inside an expression.
2
A function expression is very similar to and has almost the same syntax as, a function declaration.
3
Can be Anonymous or Named: The main difference between a function expression and a function declaration is the function name, which can be omitted in function expressions to create anonymous functions.
4
Hoisting: You cannot call a function expression before you define it. The variable is hoisted, but the function value is not assigned until the code runs.

javascript

If you want to refer to the current function inside the function body, you need to create a named function expression. This name is then local only to the function body (scope). This avoids using the deprecated arguments.callee property to call the function recursively.

Scenario Questions

0-2 years experience

Follow-up Questions