Block scope: const declaration

const is like let plus read-only

scalar values are read-only

e.g. a number

const constNum = 0; constNum = 1; assert.equal(constNum, 0);

or a string

const constString = 'I am a const'; constString = 'Cant change you?'; assert.equal(constString, 'I am a const');

complex types are NOT fully read-only

array's items can be changed

const arr = []; arr[0] = 0; assert.equal(arr[0], 42);

object's can be modified

const obj = {x: 1}; obj.x = 2; assert.equal(obj.x, 3);