Get the length of an object (ES5) :

var size = Object.keys(myObj).length;

• Basic HTML events
• Basic javascript events
• How to correctly use preventDefault(), stopPropagation(), or return false; on events

• On Chrome e.originalEvent.screenX take different values than e.originalEvent.clientX, unlike Firefox.

• https://javascript.info/promise-basics
• https://javascript.info/promise-chaining

Source

if( typeof google_step != 'undefined')
{
	// ...
}

• Basic copy with = is just a reference, not new object