What is the difference between LET and CONST in JavaScript?

_JavaScript-LET-vs-CONST.md

Code Examples for my Blog Post: What is the difference between LET and CONST in JavaScript?

block-scope-example.js

var i = 100;

{
    console.log('(A) i = ' + i); //100
}

console.log('(B) i = ' + i); //100

const-example-1-output.js

// const-example-1: output
(A) i = 50
(B) i = 100

const-example-1.js

var i = 100;

{
    const i = 50;

    console.log('(A) i = ' + i); //50
}

console.log('(B) i = ' + i); //100

const-example-2-output.js

// const-example-2: output
Uncaught TypeError: Assignment to constant variable.

const-example-2.js

var i = 0,
j = 100;

for (; i < 10; i++) {
    //j is now private to this block
    const j = 50;

    //attempt to increment j (throws a TypeError)
    j++;

    //this code never even has a chance to execute
    console.log('i =' + i + ' | j = ' + j);
}

const-example-3-output.js

i = 0 | j = 50
i = 1 | j = 50
i = 2 | j = 50
i = 3 | j = 50
i = 4 | j = 50
i = 5 | j = 50
i = 6 | j = 50
i = 7 | j = 50
i = 8 | j = 50
i = 9 | j = 50

const-example-3.js

var i = 0,
    j = 100;

for (; i < 10; i++) {
    //j is now private to this block
    const j = 50;

    //j will always be 50 in the console
    console.log('i = ' + i + ' | j = ' + j);
}

let-example-1-output.js

//let-example-1: output
(A) i = 50
(B) i = 100

let-example-1.js

var i = 100;

{
    let i = 50;

    console.log('(A) i = ' + i); //50
}

console.log('(B) i = ' + i); //100

let-example-2-output.js

i = 0 | j = 51
i = 1 | j = 51
i = 2 | j = 51
i = 3 | j = 51
i = 4 | j = 51
i = 5 | j = 51
i = 6 | j = 51
i = 7 | j = 51
i = 8 | j = 51
i = 9 | j = 51

let-example-2.js

var i = 0,
    j = 100;

for (; i < 10; i++) {
    //j is now private to this block
    let j = 50;

    //increment j
    j++;

    //j will always be 51 in the console
    console.log('i = ' + i + ' | j = ' + j);
}