var iMax = 20;

var jMax = 10;

var f = new Array();

​

for (i=0;i<iMax;i++) {

 f[i]=new Array();

 for (j=0;j<jMax;j++) {

  f[i][j]=0;

 }

}

​

var items = [

  [1, 2],

  [3, 4],

  [5, 6]

];

console.log(items[0][0]); // 1

console.log(items[0][1]); // 2

console.log(items[1][0]); // 3

console.log(items[1][1]); // 4

console.log(items);

const m = 4;

const  n = 5;

let arr = new Array(m); // create an empty array of length n

for (var i = 0; i < m; i++) {

  arr[i] = new Array(n); // make each element an array

}

console.log(arr); //  Output: [ [ <5 empty items> ], [ <5 empty items> ], [ <5 empty items> ], [ <5 empty items> ] ]

var obj = {};

​

obj['fred'] = {};

if('fred' in obj ){ } // can check for the presence of 'fred'

if(obj.fred) { } // also checks for presence of 'fred'

if(obj['fred']) { } // also checks for presence of 'fred'

​

// The following statements would all work

obj['fred']['apples'] = 1;

obj.fred.apples = 1;

obj['fred'].apples = 1;

​

// or build or initialize the structure outright

var obj = { fred: { apples: 1, oranges: 2 }, alice: { lemons: 1 } };

//2D array

let activities = [

    ['Work', 9],

    ['Eat', 1],

    ['Commute', 2],

    ['Play Game', 1],

    ['Sleep', 7]

];

let activities = [

    ['Work', 9],

    ['Eat', 1],

    ['Commute', 2],

    ['Play Game', 1],

    ['Sleep', 7]

];

Code language: JavaScript (javascript)

// multidimensional array

const data = [[1, 2, 3], [1, 3, 4], [4, 5, 6]];

let studentsData = [['Jack', 24], ['Sara', 23], ['Peter', 24]];

var grid = [];

iMax = 3;

jMax = 2;

count = 0;

​

    for (let i = 0; i < iMax; i++) {

      grid[i] = [];

​

      for (let j = 0; j < jMax; j++) {

        grid[i][j] = count;

        count++;

      }

    }

​

// grid = [

//   [ 0, 1 ]

//   [ 2, 3 ]

//   [ 4, 5 ]

// ];

​

console.log(grid[0][2]); // 4