30秒学会 JavaScript 片段 – nthArg

Creates a function that gets the argument at index n. If n is negative, the nth argument from the end is returned.

Use Array.prototype.slice() to get the desired argument at index n.

代码片段

const nthArg = n => (...args) => args.slice(n)[0];

使用样例

const third = nthArg(2);
third(1, 2, 3); // 3
third(1, 2); // undefined
const last = nthArg(-1);
last(1, 2, 3, 4, 5); // 5