Returns the n maximum elements from the provided array.
If n is greater than or equal to the provided array’s length, then return the original array (sorted in descending order).

Use Array.prototype.sort() combined with the spread operator (...) to create a shallow clone of the array and sort it in descending order.
Use Array.prototype.slice() to get the specified number of elements.
Omit the second argument, n, to get a one-element array.

代码片段

const maxN = (arr, n = 1) => [...arr].sort((a, b) => b - a).slice(0, n);

使用样例

maxN([1, 2, 3]); // [3]
maxN([1, 2, 3], 2); // [3,2]