What is the best way to merge arrays based on their indexes in Javascript?

Question

What is the best way to merge arrays based on their indexes in Javascript?

I am facing a challenge with two 2d arrays:

var ar1 = [];
var ar1[0] = [];
var ar1[0][0] = 1;
var ar1[0][1] = 2;
var ar1[1] = [];
var ar1[1][0] = 3;
var ar1[1][1] = 4;

var ar2 = [];
var ar2[0] = [];
var ar2[0][3] = 5;
var ar2[0][4] = 6;
var ar2[1] = [];
var ar2[1][5] = 7;
var ar2[1][6] = 8;

I am seeking a way to create a combined array that will appear as follows:

var ar1[0][0] = 1;
var ar1[0][1] = 2;
var ar1[1][0] = 3;
var ar1[1][1] = 4;
var ar1[0][3] = 5;
var ar1[0][4] = 6;
var ar1[1][5] = 7;
var ar1[1][6] = 8;

I attempted the following solution:

ar1.push(ar2);

However, this ends up placing the entire ar2 into the first empty row of ar1.

javascript arrays

Answer 1

Answer №1

To achieve this, iterate through each element in the second array using the forEach method, and then merge each subarray onto the corresponding index in the first array using Object.assign:

const arr1 = [];
arr1[0] = [];
arr1[0][0] = 1;
arr1[0][1] = 2;
arr1[1] = [];
arr1[1][0] = 3;
arr1[1][1] = 4;

const arr2 = [];
arr2[0] = [];
arr2[0][3] = 5;
arr2[0][4] = 6;
arr2[1] = [];
arr2[1][5] = 7;
arr2[1][6] = 8;

arr2.forEach((subarray, index) => {
  Object.assign(arr1[index], subarray);
});
console.log(arr1);

It's important to remember that using var is recommended only when defining a new variable. Avoid using sparse arrays as they can lead to unexpected behavior.

Answer 2

To achieve this, iterate through each element in the second array using the forEach method, and then merge each subarray onto the corresponding index in the first array using Object.assign:

const arr1 = [];
arr1[0] = [];
arr1[0][0] = 1;
arr1[0][1] = 2;
arr1[1] = [];
arr1[1][0] = 3;
arr1[1][1] = 4;

const arr2 = [];
arr2[0] = [];
arr2[0][3] = 5;
arr2[0][4] = 6;
arr2[1] = [];
arr2[1][5] = 7;
arr2[1][6] = 8;

arr2.forEach((subarray, index) => {
  Object.assign(arr1[index], subarray);
});
console.log(arr1);

It's important to remember that using var is recommended only when defining a new variable. Avoid using sparse arrays as they can lead to unexpected behavior.

Answer 3

Answer №2

To merge the values of two arrays, iterate through the second array and assign each value to the corresponding index in the first array. If an array is not present in the second level, use an empty array as the default.

var array1 = [],
    array2 = [];

array1[0] = [];
array1[0][0] = 1;
array1[0][1] = 2;
array1[1] = [];
array1[1][0] = 3;
array1[1][1] = 4;

array2[0] = [];
array2[0][3] = 5;
array2[0][4] = 6;
array2[1] = [];
array2[1][5] = 7;
array2[1][6] = 8;

array2.forEach((arr, i) => {
    array1[i] = array1[i] || [];
    arr.forEach((val, j) => array1[i][j] = val);
});
console.log(array1);

Answer 4

To merge the values of two arrays, iterate through the second array and assign each value to the corresponding index in the first array. If an array is not present in the second level, use an empty array as the default.

var array1 = [],
    array2 = [];

array1[0] = [];
array1[0][0] = 1;
array1[0][1] = 2;
array1[1] = [];
array1[1][0] = 3;
array1[1][1] = 4;

array2[0] = [];
array2[0][3] = 5;
array2[0][4] = 6;
array2[1] = [];
array2[1][5] = 7;
array2[1][6] = 8;

array2.forEach((arr, i) => {
    array1[i] = array1[i] || [];
    arr.forEach((val, j) => array1[i][j] = val);
});
console.log(array1);

What is the best way to merge arrays based on their indexes in Javascript?

Answer №1

Answer №2

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