ES6 Syntax

let & const

let used on variable values
const constant values

Arrow Functions

solves issues with this keyword

const myFunc = () => {

}
// shorter
const multiply number => number * 2;

Exports & Imports

1 2	import * as bundled from './app.js'; import { smith as Smith } from './app.js';

Class

class Human {
  gender = 'male';

  printGender = () => {
    console.log(this.gender);
  }
}
// property
class Person extends Human{
  name = 'Max';
  gender = 'female';

  print = () => {
    console.log(this.name);
  }
}

// usage
const myPerson = new Person();
myPerson.print();
myPerson.printGender();

Spread & Rest

Spread: Used to split up array elements OR object properties
Rest: Used to merge a list of function arguments into an array

const numbers = [1, 2, 3]
const newNumbers = [...numbers, 4]

const person = {
  name: 'Max',
};

const newPerson = {
  ...person,
  age: 28,
}

// Rest
const filter = (...args) => {
  return args.filter(el => el === 1);
}

Destructuring

Easily extract array elements or object properties and store them in variables

1
2
3

const numbers = [1, 2, 3]
[num1, , num3] = numbers;
console.log(num1, num2);

Primitive type & Reference type

const num = 1;
const num2 = num; // build a real COPY of num

// Reference type: object
const person = {
  name: 'Max',
};

const secondPerson = person; // secondPerson is another pointer to the memory

// To create a real copy of object
const secondPerson = {
  ...person
};

Array Functions

const numbers = [1, 2, 3];

// map
const doubleArray  = numbers.map((num) => {
  return num * 2;
});

// find
const findNum = numbers.find((num) => {
  return num == 2;
});

// filter
const filterNum = numbers.filter((num) => {
  return num < 3;
});

// reduce
const reducer = (accumulator, currentValue) => {
  return accumulator + currentValue;
}

numbers.reduce(reducer);