• 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

	var tmpDisable = {};
	var lastTmpDisable = {};

	lastTmpDisable = tmpDisable; // Any change made to any of these object will be on both because they're references

	// If we declare it this way a new object is created
	for(var key in tmpDisable)
	{
		lastTmpDisable[key] = tmpDisable[key]
	}

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