从Number.prototype上的方法返回数字的值？

Question

Before going in to the details of the issue I'm already fully aware of modifying built in's prototypes. This code is written in typescript.

Ok so I'm running in to an issue when I'm trying to return a number's value from a method on Number.prototype.

Here is the definition on Number.prototype:

Object.defineProperty(Number.prototype, 'tap', {
  value: function numberTap (fn: (t: number) => void): number {
    fn.call(null, this.valueOf());
    return this.valueOf();
  }
});

and the test I'm running:

describe('Number.prototype.tap((value:number) => void): number', () => {
  it('is defined', function () {
    expect(Number.prototype.tap).to.be.a('function');
  });

  it('returns the same value as its entry point in the method chain', () => {
    expect((1).tap(n => 5)).to.equal(1);
  });
});

It doesn't equal 1 but [Number 1] . If I call [Number 1].valueOf() then it returns 1 . I'm already calling this.valueOf() when returning from tap. Anyone know what's going on here.

Answer 1

Just tried the following:

Object.defineProperty(Number.prototype, 'tap', {
  value: function numberTap(fn) {
    fn.call(null, this.valueOf());
    return this.valueOf();
  }
});

typeof (1).tap(function(){})

and it runs just fine.

Answer 2

I figured it out. I was missing a require that defined Number.prototype.tap and had Object.prototype.tap already defined so it was causing this issue.