Why does JSHint throw a warning if I am using const?

When relying upon ECMAScript 6 features such as const, you should set this option so JSHint doesn’t raise unnecessary warnings.

/*jshint esnext: true */ (Edit 2015.12.29: updated syntax to reflect @Olga’s comments)

/*jshint esversion: 6 */

const Suites = {
    Spade: 1,
    Heart: 2,
    Diamond: 3,
    Club: 4
};

This option, as the name suggests, tells JSHint that your code uses ECMAScript 6 specific syntax.
http://jshint.com/docs/options/#esversion

Edit 2017.06.11: added another option based on this answer.

While inline configuration works well for an individual file, you can also enable this setting for the entire project by creating a .jshintrc file in your project’s root and adding it there.

{
  "esversion": 6
}