Concat two arrays on different indexes in javascript

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I have two arrays:

arr1 = ['1', 'x', '0', 'x']

arr2 = ['2', '5']

I want to replace the 'x' in the first array, with the numbers in the second array in the exact order so I would obtain something like this:

arr3 = ['1', '2', '0', '5']

I have no idea where to start. I've tried with concat() and slice() but with no result.

Iterate arr1 with, and use an outer counter. Whenever the value is 'x', use to counter to get the value from arr2, and increment the counter:

const arr1 = ['1', 'x', '0', 'x']

const arr2 = ['2', '5']

let counter = 0;
const result = => c === 'x' ? arr2[counter++] : c);


Array.prototype.concat(), We're going to cover different methods for combining/merging two JS arrays, OK, let's just append one array 's contents onto the other, using  The concat() method is used to join two or more arrays. This method does not change the existing arrays, but returns a new array, containing the values of the joined arrays.

You could map array 1 and check the value and take value at an index for the other array by using a clsure of the index.

var array1 = ['1', 'x', '0', 'x'],
    array2 = ['2', '5'],
    result = => v => v === 'x' ? array2[i++] : v)(0));

2 Ways to Merge Arrays in JavaScript, Now the second method is like a shortcut; you just have to store the values of two or more arrays in a different array using ellipses or spread  Here are 2 ways to combine your arrays and return a NEW array. Here are 2 ways to combine your arrays and return a NEW array. Let's look at how we do that using spread and concat.

You can do something like this

var arr1 = ['1', 'x', '0', 'x'];

var arr2 = ['2', '5'];

for(var i = 0; i < arr1.length; i++) {
  if (arr1[i] == "x") {
    arr1[i] = arr2[0];// replace 
    arr2.shift(); // delete first element


Combining JavaScript Arrays, JavaScript Array: Exercise-30 with Solution​​ Write a JavaScript function to merge two arrays and removes all duplicates elements. ES6 Version: function merge_array(array1, array2) { const result_array = []; const arr = array1. concat(array2); let len = arr. Concatenating arrays in JavaScript can be done with the concat() method. The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

If both arrays are always in correct order, this is trivial:

var arr3 = => item === 'x' ? arr2.shift() : item);

Three Ways to Combine Arrays in JavaScript, javascript documentation: Merge two array as key value pair. When we have two separate array and we want to make key value pair from that two array, we field, index) { result[columns[index]] = field; return result; }, {}) console.log(result);. Array#concat(..) is the tried and true approach for combining two (or more!) arrays. But the hidden danger is that it's creating a new array instead of modifying one of the existing ones. But the hidden danger is that it's creating a new array instead of modifying one of the existing ones.

It better using forloop than map because its faster if you have a bigger arrays


var arr1 = ['1', 'x', '0', 'x'];
var arr2 = ['2', '5'];

var counter = 0;
for(int i = 0; i < arr1.length; i++){

if(arr1[i] === 'x'){
  arr1[i] = arr2[counter];


JavaScript array: Merge two arrays and removes all duplicates , Array.concat() function is used to merge two or more arrays together. to get the elements of one array which are not present in another array using JavaScript? The concat method creates a new array consisting of the elements in the object on which it is called, followed in order by, for each argument, the elements of that argument (if the argument is an array) or the argument itself (if the argument is not an array). It does not recurse into nested array arguments.

JavaScript, Here and in other array methods, negative indexes are allowed. concat. The method arr.concat creates a new array that includes values from other arrays and The function should compare two arbitrary values and return:. Example 1: Concatenate Two Arrays using arraycopy. import java.util.Arrays; public class Concat { public static void main(String [] args) { int[] array1 = {1, 2, 3}; int[] array2 = {4, 5, 6}; int aLen = array1.length; int bLen = array2.length; int[] result = new int[aLen + bLen]; System.arraycopy (array1, 0, result, 0, aLen); System.arraycopy (array2, 0, result, aLen, bLen); System.out.println (Arrays.toString (result)); } }

JavaScript, We will explore 3 ways to combine the elements of multiple arrays into one without Make sure to follow along in the index-START.js file. The Challenge. Given two or more arrays, write a function that combines their elements into one array  In this short article, you will learn about different ways to concatenate two arrays into one in Java.. Using A Loop. The simplest way to concatenate two arrays in Java is by using the for loop:

Array methods, Check if a variable is array type with Arra Check if a variable is array type with inst Check if array.sort is case sensitive in Ja Concatenate Array elements together in Java Concatenate two dimensional array in JavaSc Create a case-insensitive comparison in Jav Create an array with different type of valu

  • @AlexandruNeagu - you're welcome :)
  • Not the best way. But the most comprensible one!