Returns the nth element of an array.

Use Array.prototype.slice() to get an array containing the nth element at the first place.
If the index is out of bounds, return undefined.
Omit the second argument, n, to get the first element of the array.

代码片段

const nthElement = (arr, n = 0) => (n === -1 ? arr.slice(n) : arr.slice(n, n + 1))[0];

使用样例

nthElement(['a', 'b', 'c'], 1); // 'b'
nthElement(['a', 'b', 'b'], -3); // 'a'