Javascript 101

// Concise Object Literal Declarations
const getMousePosition = (x, y) => ({ x, y });

// Concise Declarative Functions
const person = {
  name: "Taylor",
  sayHello() {
    return `Hello! My name is ${this.name}.`;
  }
};

class Book {
  constructor(author) {
    this._author = author;
  }
  // getter
  get writer() {
    return this._author;
  }
  // setter
  set writer(updatedAuthor) {
    this._author = updatedAuthor;
  }
}
const lol = new Book('anonymous');
console.log(lol.writer);  // anonymous
lol.writer = 'wut';
console.log(lol.writer);  // wut

// file ./math_funcs.js
const add = (x, y) => {return x + y};
const subtract = (x, y) => {return x - y};
export { add, subtract }; // can be imported in other scripts

// file ./math_default.js only has 1 export
export default function(x, y) { // without name
  return x + y;
}

// main.js
import {add, subtract } from './math_funcs.js';
import * as myMathModule from "./math_functions.js"; // everything

import anything from './math_default.js'; // from export default

function someFn() {
  if (true) {
    var localVar=1000
    console.log(localVar)      //ok
  }
  console.log(localVar)        //ok
  function nested() {
    console.log(localVar)      //ok
  }
}
console.log(localVar)      //error

function someFn() {
  if (true) {
    let localVar=1000
    console.log(localVar)      //ok
  }
  console.log(localVar)        //error
  function nested() {
    console.log(localVar)      //error
  }
}
console.log(localVar)      //error

myName = "Thi"
console.log("I'm " + myName + ".");
console.log(`I'm ${myName}.`); // ES6

function <funcName>(<para>){
  // commands
}

var a = 'Anh-Thi' + 'Dinh'; // plus the strings
a.length; // length of the string
a[0]; // first letter of the string
a[3]; // 4th letter
a[a.length - 1]; // last letter

a[0] = 'D'; // !!! CAN'T change an individual word

var arrName = ['a', 1, 'c'];
var nestedArr = [[1, 2], [3, 4]];

arrName[0] = 2; // 1st element is changed (different from string!)
nestedArr[1]; // gives [3, 4]

arrName.push(5); // add 5 at the END of an array
arrName.unshift(6); // add 6 at the BEGINNING of an array

popedElement = arrName.pop() // remove the LAST element of an array
shiftedElement = arrName.shift() // remove the FIRST element of an array

myObj.top = "T-shirt"; // Update object properties
myObj.middle = "New shoe"; // Add new properties
delete myObj.middle; // Delete a property

var alpha = {1:"A", 2:"B", 3:"C"};
value = 2;
alpha[value]; // instead of using if value==2 or switch value...

let obj = {
  name:"FreeCodeCamp",
  review:"Awesome"
};
Object.freeze(obj); // obj can't be changed

const user = {name: "Thi", age: 30};
const {name, age} = user; // name="Thi", age=30

const {name: uName, age: uAge} = user; // uName="Thi", uAge=30

const user = {
  anhThi: {
    age: 30,
    email: 'dinhanhthi@gmail.com'
  }
};
const {anhThi: {age, email}} = user;
const {anhThi: {age: userAge, email: userEmail}} = user;

const [a, b, ...arr] = [1, 2, 3, 4, 5, 7];
console.log(a, b); // 1, 2
console.log(arr); // [3, 4, 5, 7]

const profileUpdate = ({ name, age, nationality, location }) => {
  // do something with these fields
}

var ourMusic = [
  {
    "artist": "Daft Punk",
    "title": "Homework",
    "release_year": 1997,
    "formats": [
      "CD",
      "Cassette",
      "LP"
    ],
    "gold": true
  }, // first artist
  {
  ...
  } // second artist
];