Encapsulate a timestamp to date method on string prototype

Just learning React course , There is a section about DOM Of diffing Algorithm , The teacher's example shows the current time , But he didn't show it completely , But with toTimeString() , And I've encapsulated this method before ： Time stamp to format date

When I use it, I think about it , In this way, it is a function , Can it be like toTimeString In this way, it is encapsulated in the string ？ Do as you say , Knock out the following code on the browser console ：

String.prototype.toDate = function(){
    ???
}

Suddenly confused , How can I get the value ？？

Normal function calls can take values through formal parameters , But this is the way I point out , Since it was pointed out , In function scope this Is it the caller of this function, that is, this string ？

But now it has become this, How can I get its original value ？ Don't think too much. , There must be some native way to get its value , Immediately type the following code ：

String.prototype

It is as expected , I found a suspicious guy on a bunch of properties and methods of the prototype ——valueOf

'123'.valueOf() // '123'

Then the problem of getting value is solved ！！ The rest is to copy the previous code and change it a little

String.prototype.toDate = function () {
      var date = new Date(Number(this.valueOf().length == 13 ? this.valueOf() : this.valueOf() + '000'));
      let Y = date.getFullYear() + '-';
      let M = (date.getMonth() + 1).toString().padStart(2, '0') + '-';
      let D = (date.getDate()).toString().padStart(2, '0') + ' ';
      let h = (date.getHours()).toString().padStart(2, '0') + ':';
      let m = (date.getMinutes()).toString().padStart(2, '0') + ':';
      let s = (date.getSeconds()).toString().padStart(2, '0');
      return Y + M + D + h + m + s;
    }

  In this way, you can point out the formatting time happily   ~·o·~

Of course ,Number Type needs to be transformed first , I won't give it Number Another prototype