CODEWITHSUNDEEP
javascriptarrays
RandomStacker
RandomStacker

Reputation: 115

How to swap the place of given index numbers in arrays (javascript)

I am having trouble with an excercise I have from school.

We have to swap two numbers in an array given two indexes. Here are the test cases.

Here is my code:

function swap(xs, i, j) {
    var copyxs = xs.slice(0);
    for (var a = 0; a < xs.length - 1; a++) {
        if (xs.indexOf(copyxs[a]) == i) {
            xs[a] = copyxs[j];
        }
        if (xs.indexOf(copyxs[a]) == j) {
            xs[a] = copyxs[i];
        }
    }
    return xs;
}

Upvotes: 1

Views: 104

Answers (3)

kevin ternet
kevin ternet

Reputation: 4612

In case your teacher doesn't need you to modify input array you could do this with a map.

var input = [1,2,3,4,5,6];
    var swap = (xs, i, j) => xs.map((x,index,arr) => {
      if (index === i) return arr[j];
      if (index === j) return arr[i];
      return x;
    });
    console.log(swap(input, 2, 4));
Or in a old function :

var input = [1,2,3,4,5,6];
    function swap(xs, i, j) {
      return xs.map((x,index,arr) => {
        if (index === i) return arr[j];
        if (index === j) return arr[i];
        return x;
      });
    }
    console.log(swap(input, 2, 4));

Upvotes: 1

hackerrdave
hackerrdave

Reputation: 6706

No need to slice array, you can just reassign the values at the given indices:

function swap(arr, i, j) {
  var temp = arr[i]; //temporarily store original value at i position
  arr[i] = arr[j]; //reassign value at i position to be value at j position
  arr[j] = temp; //reassign value at j position to original value at i position
  return arr;
}

Upvotes: 1

Supradeep
Supradeep

Reputation: 3266

As you have the indexes of the array that needs to be swapped, you don't have to slice and loop through the array elements to do that. Just keep one of the index values in a temp variable and re-assign the values as shown below : 

function swap (xs, i, j){
  var temp = xs[j];
  xs[j] = xs[i];
  xs[i] = temp;
  return xs;
}


console.log(swap([1,2,3], 0, 1))

Upvotes: 1

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