merge-class-names/src/index.js

A function that merges given class names, no matter their format: string with single or multiple class names or an array of class names. Filters out invalid class names as well.

export default function mergeClassNames() {
  return Array.prototype.slice.call(arguments).reduce(
    (classList, arg) => classList.concat(arg),
    [],
  ).filter((arg) => typeof arg === 'string').join(' ');
}