rotate-words-inplace.js

const rotateWords = function(arr) {
    rotateWords.reverse(arr, 0, arr.length-1)

    let firstSpaceIndex = arr.indexOf(" ")
    let secondSpaceIndex = arr.indexOf(" ", firstSpaceIndex + 1)

    rotateWords.reverse(arr, 0, firstSpaceIndex - 1)
    rotateWords.reverse(arr, firstSpaceIndex + 1, secondSpaceIndex - 1)
    rotateWords.reverse(arr, secondSpaceIndex + 1, arr.length - 1)

    return arr
}

rotateWords.reverse = function(arr, from, to) {
    while ( from < to ) {
        [ arr[to], arr[from] ] = [ arr[from], arr[to] ]
        from++
        to--
    }
}

console.log(rotateWords("perfect makes practice".split("")).join(""))