Today, I learned all about functions and different attributes such as: - Scopes of functions - Global and Function scopes
Global scopes: Global scopes are created on the window object. Any variable declared in the global scope can be accessed anywhere.
Function scopes: Function scopes apply to variables created inside a function. If we try to access the variable outside the function, we will get a 'Reference Error'.
Variables declared with 'const' and 'let' keywords are block scoped, meaning they are accessible only within the block whereas variables declared with 'var' keyword is function scoped.
//Declaring a global function variable called x
let x = 10;
//referencing 'x' in a global scope
console.log(x, 'in global scope'); //10 'in global';
//referencing 'x' inside a function
function run(){
console.log(x, 'in function scope'); //10 'in function';
}
run();
//referencing 'x' inside a block
if(true){
console.log(x, 'in block scope'); //10 'in block'
}
//Declaring a variable in a function scope
function add() {
const y = 50;
console.log(x + y, 'in function scope'); // 60 'in function scope'
}
add();
//If we try to access 'y' outside the function scope, we will get a 'Uncaught Reference Error'
console.log(y); //Uncaught ReferenceError: y is not defined
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// An If statement is a block
if(true) {
console.log(y); //10
const a = 100
console.log(a + y) //110;
}
//If we try to access 'a' outside the block scope, we will get an ReferenceError
console.log(a); //Uncaught Reference Error
//A loop is a block
for(let i = 0; i < = 10; i++){
console.log(i); //1, 2, 3, 4, 5, 6, 7, 8, 9, 10
}
//Difference between 'var', 'let' and 'const'
//var is function scoped, meaning it can be referenced from anywhere
if(true){
const a = 100;
let b = 200;
var c = 300;
}
console.log(a); //Uncaught ReferenceError;
console.log(b); //Uncaught ReferenceError;
console.log(c); //300 'because var is accessible outside a block scope'
| Category | HTML / JS / CSS |
| Credits | NA |
| Date | February 10th, 2025 |
| Codepen | NA |