How to create a function that accepts a single argument in JavaScript

In this Article we will go through how to create a function that accepts a single argument only using single line of code in JavaScript. This is a one-line JavaScript code snippet that uses one of the most popular ES6 features => Arrow Function.

Let's define this short function:

const unary = fn => arg => fn(arg);

['1', '2', '3', '4', '5'].map(unary(parseInt));     // [1, 2, 3, 4, 5]