D2: Javascript Fundamentals

*learned basic velog markup
new q: 1) how to write french accents in a string, 2) what exactly is node.js?

more:

// Nan: Not A Number 
// `return` can be followed by any operation
// template literal: you can change lines! 
// == -> useless!
// falsey => treated as false 
// null - when you want to deliberately specify that it's empty. vs. undefined 

JS runtime environments

• (outside webbrowser)
  • Node.js
  • stackblitz (VM): enables REPL (Read, Evaluate, Print Loop)

data/variable type

*important because you can use functions/methods just reserved for those specified types

• Number
  • math.floor(), math.ceil(), math.round(), math.abs(), math.sqrt(), math.pow()

  • mathpow(2, 5) // returns 2^5
    5**7;

• String
  • '+' -> turns everything into a string (ex. 1 + "1" = 11)
  • length, index
  • toLowerCase(), toUpperCase(), concat(), slice()
  • indexOf(): where the first letter of the value is located within the string
    • index starts at 0
  • includes(): see if the string includes the value

  • 'javascript'.length();
     'hello'.concat('benji'); // 'hello benji'
     'hello world'.slice(0, 5); // 'hello' 
     'where is benji'.indexOf('benji'); // 9

• Boolean
  • falsy (false, 0, -0, 0n, "", '', ``, null, undefined, NaN), truthy
  • strict comparisons: ===, !==
  • loose comparisons: ==, !=
    • 12 == '12' //true
  • OR, AND, NOT

    • true || false // true
      false && true // false 
      !'' // true
      !'codestates' // false

variables

• 'declaration', 'assignment' can be done at the same time
• 'expressions' use variables for operations(?)
• useful for avoiding repetitive tasks (e.g. replacing values manually)
• unassigned variables get auto-assigned as 'undefined'
• const stops you from reassigning the variable
• var appeared before let/const. avoid using it, problematic
• naming conventions
  - $love, _love
  - MyLove: PascalCase, my_love: snake_case, myLove = camelCase
• template literal
  - enables you to insert a variable inside a string -> super readable!

//practice 
console.log(Math.floor(1843.123));
console.log(Math.sqrt(4));
console.log(Math.pow(3, 4));
console.log('최초의 JavaScript는 Netscape의 Brendan '.length);
console.log('where is benji'.indexOf('benji'));
console.log(!'codestates');


let FirstName = 'Kylian';
let MiddleName = 'A';
let LastName = 'MBappe';

console.log(`${FirstName} ${MiddleName} ${LastName}`);
console.log(`My name is ${FirstName} ${LastName}, and my middle name is ${MiddleName}.`);