ES 6

Let vs Var vs Cost

• Var

function sayHello() {
    for(var i = 0; i < 5; i++) {
        console.log(i)
    }
    console.log(i)
}

sayHello();

• Let

function sayHello() {
    for(let i = 0; i < 5; i++) {
        console.log(i)
    }
    console.log(i)
}

sayHello();

• Const

function sayHello() {
    for(const i = 0; i < 5; i++) {
        console.log(i)
    }
    console.log(i)
}

sayHello();