JavaScript: Move an array element from one position to another

JavaScript Array: Exercise-38 with Solution

Move Array Element

Write a JavaScript function to move an array element from one position to another.

Test Data:
console.log(move([10, 20, 30, 40, 50], 0, 2));
[20, 30, 10, 40, 50]
console.log(move([10, 20, 30, 40, 50], -1, -2));
[10, 20, 30, 50, 40]

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to move an element within an array from the 'old_index' to the 'new_index'
function move(arr, old_index, new_index) {
    // Adjust negative indices to the equivalent positive indices
    while (old_index < 0) {
        old_index += arr.length;
    }
    while (new_index < 0) {
        new_index += arr.length;
    }

    // If 'new_index' is beyond the array length, extend the array with undefined elements
    if (new_index >= arr.length) {
        var k = new_index - arr.length;
        while ((k--) + 1) {
            arr.push(undefined);
        }
    }

    // Remove the element at 'old_index' and insert it at 'new_index'
    arr.splice(new_index, 0, arr.splice(old_index, 1)[0]);

    // Return the modified array
    return arr;
}

// Output the result of moving the element at index 0 to index 2
console.log(move([10, 20, 30, 40, 50], 0, 2));

// Output the result of moving the last element to the second-to-last position
console.log(move([10, 20, 30, 40, 50], -1, -2));

Output:

[20,30,10,40,50]
[10,20,30,50,40]

Flowchart:

ES6 Version:

// Function to move an element within an array from the 'old_index' to the 'new_index'
function move(arr, old_index, new_index) {
    // Adjust negative indices to the equivalent positive indices
    while (old_index < 0) {
        old_index += arr.length;
    }
    while (new_index < 0) {
        new_index += arr.length;
    }

    // If 'new_index' is beyond the array length, extend the array with undefined elements
    if (new_index >= arr.length) {
        let k = new_index - arr.length;
        // Use a loop to push undefined elements to the array
        while ((k--) + 1) {
            arr.push(undefined);
        }
    }

    // Remove the element at 'old_index' and insert it at 'new_index'
    arr.splice(new_index, 0, arr.splice(old_index, 1)[0]);

    // Return the modified array
    return arr;
}

// Output the result of moving the element at index 0 to index 2
console.log(move([10, 20, 30, 40, 50], 0, 2));

// Output the result of moving the last element to the second-to-last position
console.log(move([10, 20, 30, 40, 50], -1, -2));

Live Demo :

See the Pen JavaScript - Move an array element from one position to another-array-ex- 38 by w3resource (@w3resource) on CodePen.

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