add hours to date in typescript code example

Example 1: add 2 for hours in date timestamp js

Date.prototype.addHours= function(h){
    this.setHours(this.getHours()+h);
    return this;
}

alert(new Date().addHours(4));

Example 2: javascript get 1 hour from now

Date.prototype.addHours = function(h) {
  this.setTime(this.getTime() + (h*60*60*1000));
  return this;
}