JavaScript

• JavaScript


  programming language used to create and control dynamic website content i.e. anything that moves, refreshes, or otherwise changes on your screen without requiring you to manually reload a web page
• Variables


  a name of storage location. the actual value of a variable can be changed at any time
• Primitive Data Types

  String

  number

  boolean

  undefined

  null

  symbol

  bigint
• Non-Primitive Data Types

  object

  array
• string data type


  const name ="js string";
• number data type


  const num = 20;
• boolean data type


  const t = true;

  const f = false;
• undefined data type


  let u;

  const t = undefined;

  const u = null;
• symbol data type


  const a = symbol("a");

  const b= symbol("a");

  console.log(a===b); // false
• object data type


  let myObj = {

  "height-cm": 175,

  "weight-lbs": 275,

  "distance-km": 7

  };
• array data type


  // array with the same data type

  let food = ["pizza", "burgers", "fries", "cake"]

  // array with different data types

  let order = [25, "burgers", 50.99, true];
• document object model 


  also known as DOM, allows java to remove existing HTML elements and attributes, modify CSS properties, react to all existing HTML events on the page
• document.getElementbyID();


  JavaScript can access HTML and CSS through: ID
• document.getElementsByClassName();


  JavaScript can access HTML and CSS through: Class
• document.getElementsByTagName();


  JavaScript can access HTML and CSS through: Tag Name (<div>, <p>, <a>)
• document.querySelector();


  JavaScript can access HTML and CSS through: CSS Selectors
• document.getElementsByName();


  JavaScript can access HTML and CSS through: Name Attribute