Two Array Result Make New Array in Javascript

Question

This are my two data arrays:

var array1 = ["test","test1","test2"];
var array2 = ["test3","test4","test5"];

I need to concact the array to get the following result:

array3["test","test3","test1","test4","test2","test5"]

How can I archive this?

Answer 1

Considering, both arrays can have different number of elements

var array1 = ["test","test1","test2"];
var array2 = ["test3","test4","test5"];
var maxLength = Math.max(array1.length, array2.length)
var array3 = [];
for (var index=0; index < maxLength; index++) {
 if (index < array1.length)
 array3.push(array1[index]);
 if (index < array2.length)
 array3.push(array2[index]);
}
console.log(array3);

• gvn: thanks for the help... that array1,array2 are dynamically formed one. and last array3 also dynamic then.. it's will be work
• Bilal Siddiqui: happy to help :)

Answer 2

You could transose the arrays and flat the result.

var array1 = ["test", "test1", "test2"],
 array2 = ["test3", "test4", "test5"],
 result = [array1, array2]
 .reduce((r, a) => a.map((v, i) => [...(r[i] || []), v]), [])
 .reduce((a, b) => a.concat(b));
console.log(result);

Answer 3

I would recommend array.reduce() to achieve this concisely.

let array1 = ["test", "test1", "test2"];
let array2 = ["test3", "test4", "test5"];
const weaveArrays = (array1, array2) => {
 // Only allow arrays of same length
 if (array1.length === array2.length) {
 return array1.reduce((acc, v, i) => {
 acc.push(v, array2[i]);
 return acc;
 }, []);
 } else {
 console.warn('Arrays passed to "weaveArrays" must be of equal length');
 return [];
 }
}
console.log(weaveArrays(array1, array2));

• Bilal Siddiqui: What if array1 has 2 elements and array2 has 4 ?
• Miroslav Glamuzina: In my first example, it has a check if the element exists and safely pushes the value. In my current iteration, I only allow arrays of the same length. Depends what OP wants

Answer 4

You can find the minimal length, the process the element with index less minimal length, then attach the element from the minimal length index.

var array1 = ["test","test1","test2","test6"];
var array2 = ["test3","test4","test5"];
var array1_length = array1.length;
var array2_length = array2.length;
var minLength = Math.min(array1_length,array2_length);
var result = [];
for (var index=0; index < minLength; index++){
 result.push(array1[index]);
 result.push(array2[index]);
}
if(array1_length > array2_length){
 result = result.concat(array1.slice(index));
}
if(array2_length > array2_length){
 result = result.concat(array2.slice(index));
}
console.log(result);