JavaScript ES6

Variable

• let and const
  • Has block scope. Cannot be accessible from outside code block

let name = "Mac"
if(name === "Mac") {
    let greeting = "Hello"
}
console.log(greeting) // ReferenceError: greeting is not defined

Function

• Can have default variable

function hello(msg = "Hello") {
    return msg;
}
console.log(hello()) // Print out "Hello"

Template string

let name = "Mac"
let msg = `Hello. My name is ${name}`

Arrow function

let add = (a, b) => a + b
console.log(add(1, 2))

Looping

var names = ["Java", "Python", "JavaScript", "C#"]

// Use in
for(let i in names) {
    console.log(names[i])
}

// Use of 
for(let name of names) {
    console.log(name)
}

// Use forEach
names.forEach(name => {
    console.log(name)
})

Collection

• Map

var userMap = new Map();
userMap.set('Mac', '[email protected]')
userMap.set('Java', '[email protected]')
for(let [k, v] of userMap) { 
    console.log(k + ' = ' + v)
}

• Set

var numbers = new Set()
numbers.add(1)
numbers.add(2)
numbers.add(1)
numbers.add(3)
for(let n of numbers) {
    console.log(n);
}

Module

• CommonJS

// greeting.js
exports.sayHello = function hello() {
    return "Hello";
};

// app.js 
let greeting = require('./greeting');
console.log(greeting.sayHello())

• ES6 Module