Gamepad.mapping

The Gamepad.mapping property of the Gamepad interface returns a string indicating whether the browser has remapped the controls on the device to a known layout.

Currently there is only one supported known layout–the standard gamepad. If the browser is able to map controls on the device to that layout the mapping property will be set to the string standard.

readonly    attribute DOMString           mapping;

var gp = navigator.getGamepads()[0];
console.log(gp.mapping);

A string.

Using the Gamepad API