Array

• Arrays: ordered collections of values
  • List of comments on IG post
  • Collection of levels in a game
  • songs in a playlist
• Creating Arrays

let students = [];  //empty array

let colors = ['red', 'orange', 'yellow']; // strings

let lottoNums = [19,22,34];  //numbers

let stuff = [true, 68, 'cat', null];   //mixed array

• arrays can be modified

let colors = ['red', 'blue', 'green'];

color[0] = 'red';

color[3] = 'blue';

• Array methods
  • push, add to end
  • pop, remove from end
  • shift, remove from start
  • unshift, add to start
  • concat, merge arrays
  • includes, look for a value
  • indexOf, just like string.indexOf
  • join, creats a string from an array
  • reverse, reverses an array
  • slice, copies a portion on an array
  • splice, removes/replaces elements
  • sort, sort an array
• Use const to define an array, as long as the reference remains the same, we can change the values of an array

• const Eggs = ['brown', 'brown'];
  Eggs.push('purple');
  Eggs[0] = 'green';
  
  
  
  Eggs = ['nlue', 'pink']; //ERROR ! the reference was changed

   

• nested arrays

  const board = [
       ['O', null, 'X'],
       ['H', 'A', 'N'],    
  ]
  
  
  board[1][0] = 'H'