How to move last item to start of array in Javascript-CodePudding

How can I move the last item in an array to the start?

So, for example, I have the array ["a", "b", "c"]. How do I make it ["c", "a", "b"]?

CodePudding user response：

let a = ["a", "b", "c"]

a.unshift(a.pop())

CodePudding user response：

Array.slice() is a good start, and it doesn't modify the original array. Here's a small algorithm using `Array.slice() and supporting wrap around:

let rotatingSlice = (a, start, end) => {
    if (start < 0 && end > a.length)
        return a.slice(start).concat(a.slice(0, end));
    if (start < 0)
        return a.slice(start).concat(a.slice(0, end));
    else if (end > a.length)
        return a.slice(start).concat(a.slice(0, end % a.length));
    else
        return a.slice(start, end);
};

let array = [0,1,2,3,4,5,6,7];

console.log(rotatingSlice(array, 0, 3)) // 1st 3 elements
console.log(rotatingSlice(array, -3, 0)) // last 3 elements
console.log(rotatingSlice(array, -3, 3)) // last 3 and 1st 3 elements
console.log(rotatingSlice(array, 4, 4   array.length)) // the array starting at the middle