JavaScript Hoisting

JS Hoisting

Hoisting is a process where variable & function declarations are moved to the top of their scope during code execution. It allows you to use variables and call functions before they are defined in the code. However, only the declarations are hoisted, not the assignments/initialization. Understanding hoisting helps in writing code that works as expected.

JS Hoisting (Variables)

Hoisting with let, const & var differs:

console.log(x); // undefined
console.log(y); // Error: Cannot access 'y' before initialization
console.log(z); // Error: Cannot access 'z' before initialization

var x = 10;
let y = 30;
const z = 50;

The variable will be undefined until the line where it is initialized is reached.

JS Hoisting (Functions)

Function hoisting means that you can call a function before it is declared in your code, and it will still work.

myFunction(); // Hi from suwi

function myFunction() {
    console.log('Hi from suwi');
}

Function expressions & class expressions are not hoisted.

03 January Tags : coding , javascript