Create a 2D array filled with specific value in JavaScript

This post will discuss how to create a 2D array pre-filled with a specified value in JavaScript.

To create a 2D array of fixed dimensions initialized with a specified value, you can use any of the following methods:

1. Using Array constructor

In JavaScript, 2D arrays can be easily created using the array constructor and the for-loop. To initialize it with the specific value, use fill() method.

const R = 3, C = 4;

const val = 1;

var arr = Array(R);

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

arr[i] = Array(C).fill(val);

}

console.log(arr);

Output: [ [ 1, 1, 1, 1 ], [ 1, 1, 1, 1 ], [ 1, 1, 1, 1 ] ]

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2. Using `Array.from()` function

The Array.from() method creates a new array instance from the specified array and optionally map each array element to a new value. This can be used as follows for creating a 2D array:

const R = 3, C = 4;

const val = 1;

var arr = Array.from({ length: R }, () => Array.from({ length: C }, () => val));

console.log(arr);

Output: [ [ 1, 1, 1, 1 ], [ 1, 1, 1, 1 ], [ 1, 1, 1, 1 ] ]

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You can simplify this to the following code:

const R = 3, C = 4;

const val = 1;

var arr = Array.from(Array(R), () => Array(C).fill(val));

console.log(arr);

Output: [ [ 1, 1, 1, 1 ], [ 1, 1, 1, 1 ], [ 1, 1, 1, 1 ] ]

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3. Using `Array.prototype.map()` function

Alternatively, you can directly call the map() function on the array, as shown below:

const R = 3, C = 4;

const val = 1;

var arr = Array(R).fill().map(() => Array(C).fill(val));

console.log(arr);

Output: [ [ 1, 1, 1, 1 ], [ 1, 1, 1, 1 ], [ 1, 1, 1, 1 ] ]

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4. Using array literal notation

Finally, 2D arrays can also be created using the array literal notation. The following code example shows how to implement this using two loops:

const R = 3, C = 4;

const val = 1;

var arr = [];

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

arr[i] = [];

for (var j = 0; j < C; j++) {

arr[i][j] = val;

}

console.log(arr);

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That’s all about creating a 2D array filled with the specified value in JavaScript.

Create a 2D array filled with specific value in JavaScript

1. Using Array constructor

2. Using Array.from() function

3. Using Array.prototype.map() function

4. Using array literal notation

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2. Using `Array.from()` function

3. Using `Array.prototype.map()` function