Consider following array in Javascript:

var array1 = ['S', 'T', 'A', 'C', 'K', 'O', 'V', 'E', 'R', 'F', 'L', 'O', 'W'];

Now I want to replace all the elements at once from index 3 to 9 in following way:

array1 = ['S', 'T', 'A', 'X', 'X', 'X', 'X', 'X', 'X', 'X', 'L', 'O', 'W'];

Is it possible to achieve in javascript ?

Note: I want to perform following operation using array only

Consider following array in Javascript:

var array1 = ['S', 'T', 'A', 'C', 'K', 'O', 'V', 'E', 'R', 'F', 'L', 'O', 'W'];

Now I want to replace all the elements at once from index 3 to 9 in following way:

array1 = ['S', 'T', 'A', 'X', 'X', 'X', 'X', 'X', 'X', 'X', 'L', 'O', 'W'];

Is it possible to achieve in javascript ?

Note: I want to perform following operation using array only

• javascript
• arrays

• 2 array1.forEach((a,b,c)=>array1[b]=(b<9 && b>2)?'X':a); – dandavis Commented Oct 31, 2021 at 5:47
• @dandavis your boundaries are off, 9 is inclusive – Samathingamajig Commented Oct 31, 2021 at 5:50
• touchè. it's late here, but the main point is closure-ing the object to be mutated (array1) in the iteration callback – dandavis Commented Oct 31, 2021 at 5:51

4 Answers 4

Use Array.fill()

var array1 = ['S', 'T', 'A', 'C', 'K', 'O', 'V', 'E', 'R', 'F', 'L', 'O', 'W'];

array1.fill('X', 3, 10)

console.log(array1)

Use array splice() method

var array1= ['S', 'T', 'A', 'C', 'K', 'O', 'V', 'E', 'R', 'F', 'L', 'O', 'W'];
// At position 3, delete 7 and add 7 elements: 
array1.splice(3, 7, "X","X","X","X","X","X","X");

console.log(array1);

One way is with Array.prototype.map:

This loops through every index of the array, and if the index is between 3 and 9 (inclusive), set it to 'X', otherwise keep it as the original chr (character)

var array1 = ['S', 'T', 'A', 'C', 'K', 'O', 'V', 'E', 'R', 'F', 'L', 'O', 'W'];

var array2 = array1.map((chr, idx) => 3 <= idx && idx <= 9 ? 'X' : chr);

console.log(array2);

It sure does.

const arr = ['a', 'b', 'c', 'd', 'e']

function replaceWithX(start, end) {
  for (let i = start; i <= end; i++) {
    arr[i] = 'x'
  }
}

replaceWithX(1, 3)

console.log(arr) // ["a", "x", "x", "x", "e"]