Javascript function accepts both arrays and strings as parameter

Question

I have this code:

    var showRegion = function(key) {
        if (key in regionOptions) {
            var entry       = regionOptions[key];
            var builder     = entry.builder;
            var layoutObj   = entry.layoutObj;
            var viewStarter = entry.viewStarter;

            var view = new builder();
            logger.info('Controller.' + key + ' => CreateAccountLayoutController');
            Controller.layout[layoutObj].show(view);
            view[viewStarter]();
        }
    };

What I need is that the parameter should be able to accept an array or a string, and should work either way.

Sample function calls:

showRegion('phoneNumberRegion');
showRegion(['phoneNumberRegion', 'keyboardRegion', 'nextRegion']);

Answer 1

This post is old, but here is a pretty good tip:

function showRegions(keys) {
  keys = [].concat(keys)
  return keys
}

// short way
const showRegions = key => [].concat(keys)

showRegions(1) // [1]
showRegions([1, 2, 3]) // [1, 2, 3]

Answer 2

var showRegion = function(key) {
    if (typeof key === 'string')
         key = [key];
    if (key in regionOptions) {
       ...

No need to make a code for each case, just convert key string into an array of one element and the code for arrays will do for both.