CodeWars/4kyu/remove_zeros/solution.js

function swap(array, i, j) {
    let temporary = array[i];
    array[i] = array[j];
    array[j] = temporary;
}

function removeZeros(array) {
    // Sort "array" so that all elements with the value of zero are moved to the
    // end of the array, while the other elements maintain order.
    // [0, 1, 2, 0, 3] --> [1, 2, 3, 0, 0]
    // Zero elements also maintain order in which they occurred.
    // [0, "0", 1, 2, 3] --> [1, 2, 3, 0, "0"]

    // Do not use any temporary arrays or objects. Additionally, you're not able
    // to use any Array or Object prototype methods such as .shift(), .push(), etc

    // the correctly sorted array should be returned.

    for (let i = array.length - 2; i > -1; i--) {
        if (array[i] === 0 || array[i] === '0') {
            for (let j = i; j < array.length - 1 && array[j + 1] !== 0 && array[j + 1] !== '0'; j++) {
                swap(array, j, j + 1);
            }
        }
    }

    return array;
}