Ruby vs JS vs ES6

syntax.md

Variables

Ruby

Name a value.

color = "red"

JavaScript

Declare a variable (var) before you can assign it a value.

var color = 'red';

// or

var color;
color = 'red';

ES6

Apart from declaring global variables with var, you can declare local variables with let, and constants (variables that do not change after they were assigned) with const.

let color
color = 'red'
color = 'blue'

const red = 'red'
red = 'blue' # error

Functions

Ruby

def say(sentence)
  puts sentence
end

say "Hello"
#=> "Hello"

JavaScript

function say(sentence) {
  console.log(sentence);
}

// or same:

var say = function(sentence) {
  console.log(sentence)
};

say("Hello");
//=> "Hello"

ES6

const say = (sentence) => {
  console.log(sentence)
}

say("Hello")
//=> "Hello"

Hashes vs Objects

Ruby Hash

player = {
  name: "Bram",
  points: 0
}

puts player[:name]
#=> "Bram"

JavaScript Object

var player = {
  name: "Bram",
  points: 0
};

console.log(player.name);
//=> "Bram"

ES6 Objects

Object destruction

const player = {
  name: "Bram",
  points: 0
}

const { name } = player

console.log(name)
//=> "Bram"

Combining vars into Objects

const name = "Bram"
const points = 0

const player = {
  name,
  points
}

console.log(player.name)
//=> "Bram"

Object assign

Object.assign can be used to extend an Object with another Object.

const score = {
  points: 0
}

let player = { name: 'Bram' } // note: const player would give an error below!

Object.assign(player, score)

console.log(player.score)
//=> 0

console.log(player.name)
//=> "Bram"

Object.assign can be used to create new Objects from 2 or more other Objects, if we pass in a new, empty object as the first value ({}).

const score = {
  points: 0
}

const player = { name: 'Bram' } // here const will not give an error, because we're not mutating below!

newPlayer = Object.assign({}, score, player)

console.log(newPlayer.score)
//=> 0

console.log(newPlayer.name)
//=> "Bram"