We can do better.

The above snippet would get the job done, but requires extra space with the new temp array.

Without a temp array, we'll need to change the position of elements in the array in-place. This means that we'll need to mutate the array's elements directly. This requires us to keep track of indexes.

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const arr = [1, 0, 2, 0, 4, 0];

const nonZeros = [1, 2, 4]