How to replace one element of array inside loop

April 15, 2023

There is an array arr = [1, 2, "a", 4, 5];. Using loop (for…of) every element of array must be pushed inside another empty array result = [];.

But, inside arr there is an element that needed to be replaced inside loop. Here, we need to replace string "a" with number 3 and than push it inside array result.

In the end we need to get an array result = [1, 2, 3, 4, 5];. As you can see string "a" was replaced and instead number 3 was pushed.

!Important initial array arr shouldn’t be mutated and loop is a required condition.

Example:

const arr = [1, 2, "a", 4, 5];
const result = [];

for(let elem of arr) {
  if(typeof elem === "string") {
    // changing elem to number 3 and pushing it into result array instead of "a"
  }
// ...
}

Tried use several different array methods, but it didn’t help.

>Solution :

You can replace the string "a" with the number 3 and push every element into a new array using the for…of loop as follows:

const arr = [1, 2, "a", 4, 5];
const result = [];

for (let elem of arr) {
  if (typeof elem === "string" && elem === "a") {
    // replace "a" with number 3 and push it into the result array
    result.push(3);
  } else {
    // push the current element into the result array
    result.push(elem);
  }
}

console.log(result); // [1, 2, 3, 4, 5]