如何将最后一项移动到 Javascript 中的数组开头

Question

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"] ?

Answer 1

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

a.unshift(a.pop())

Answer 2

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