difference between var and let
var is function scoped and let is block scoped. Let's say you have:
function understanding_var() {
if (1 == 1) {
var x = 5;
console.log('the value of x inside the if statement is ' + x);
}
console.log(x);
}
//output: the value of x inside the if statement is 5
5
function understanding_let() {
if (1 == 1) {
let x = 5;
console.log('the value of x inside the if statement is ' + x);
}
console.log(x);
}
//output: the value of x inside the if statement is 5
Uncaught ReferenceError: x is not defined
var is defined throughout the entire function, even if it's inside the if
statement, but the scope of let is always within the curly braces, not outside
it, even if the conditional statement is inside the function.