DEV Community

Kaziu
Kaziu

Posted on

Hoisting in javascript. Magic of declare order

#javascript #beginners

What is hoisting ??

a variable can be used before it has been declared because it stores in memory

for example

💎 function 

b(); function b(){ console.log('foo'); } // "foo"  // ✅ thanks to hoisting, function has stored in memory before declaring
Enter fullscreen mode Exit fullscreen mode

▼ But arrow function isn't like that

arrFn(); const arrFn = () => { console.log('arrow!!'); } // 🔥 Uncaught ReferenceError: Cannot access 'arrFn' before initialization
Enter fullscreen mode Exit fullscreen mode

💎 variable 

console.log(b) var b = 10; // "undefined" // ✅ default initialization of the var is undefined. // ❗ initial value = undefined
Enter fullscreen mode Exit fullscreen mode

the case of const and let

console.log(NAME) // 🔥 Throws ReferenceError exception as the variable value is uninitialized const NAME = 'kaziu'
Enter fullscreen mode Exit fullscreen mode 
console.log(count) // 🔥 Throws ReferenceError exception as the variable value is uninitialized let count = 2
Enter fullscreen mode Exit fullscreen mode

Top comments (0)