Next Generation Javascript

1. === and ==
　=== checks both type and value while == only checks value

2. Spread and Rest
    Spread: 

1 const oldArray = [1, 2, 3];
2 const newArray = [...oldArray, 4];
3 console.log(newArray);  // Output [1, 2, 3, 4]

     Rest:

1 const sortFunction = (...arg) => {
2   return arg.sort();
3 }
4 
5 console.log(sortFunction(2, 3, 1));  // Output [1, 2, 3]

3. const and let
    const variable can be set only one and can not be modified
    let variable can be modified

4. Export and import
    Each file can have only one default export
    For default export, we can use alternative name when importing it in another file:

//File: constant.jsx
default export const defaultNum = 1;
export const num = 2;

//File: import.jsx
import {num as normal} from "./constant.jsx";
import defaultNum from "./constant.jsx";  // defaultNum is imported
import alterNum from "./constant.jsx";  // defaultNum is imported

5. Destructing

1 const numbers: number[] = [1, 2, 3];
2 [num1, num2] = numbers;
3 console.log(numbers);
4 console.log(num1, num2); // Output 1, 2
5 [num1, ,num3] = numbers;
6 console.log(num1, num3); // Output 1, 3