Speed of comparing to null vs undefined in JavaScript

Question

I have just run a very simple JavaScript performance test (don\'t ask why). The test declares a variable, but doesn\'t assign anything to it:

var x;

Answer 1

I recently discovered that this:

 if (typeof this._minLat === 'undefined') {
   this._minLat = Math.min(...this.points.map(point => point.lat));
 }
 return this._minLat;

seems to be many times faster than this:

 return  this._minLat || Math.min(...this.points.map(point => point.lat));