Lost this context

[hax]

const a = {
	_b: 1,
	b() {
		return this._b
	}
}

console.log(a.b()) // 1

console.log(safeTouch(a).b()()) // undefined or type error (strict mode)

[EnixCoda]

Hi @hax or 贺老?

I'm sorry that preserving this context might not be possible under current design of safe-touch.

Let me explain:

As you already know, if you want to retrieve property, apply the wrapped value as a function, e.g. safeTouch(a).b(). There is an explicit function call. In fact, every step in the property chain is a function call.

Then let's add such function to the snippet you provided:

function test() {
  return a.b
}

test() // undefined

Now we have proved that function returned from other scope could not preserve this context, even if it tried to chain.

Some people might ask - what about use bind/apply/call?

There does exist other libs that was implemented in that way, but they will create extra function, which is against one of design principles of safe-touch, i.e. safeTouch(original).key() === original.key.

This principle keeps safe-touch pure and simple.

But I have to admit: one the original goal of safe-touch was, if all property exists, user should be able to touch the object as if it was not wrapped by safe-touch. That is, safeTouch(a).b()() === 1 in the case of your snippet.

Any alternative lib choices?

Use safe-navigation-js.
It's quite similar to safe-touch, except

1. Retrieves property value with .$, in a property way. If you have an object with exactly $ property on it, life gets hard.
2. It binds this for function. safeNavigation(a).b.$ !== a.b.

How much do we need that functionality?

In my daily work, I don't write objects with function properties with this in it and use it in the way like obj.func().

If I had to, I'd write arrow functions, which works with safe-touch.

IMOP, the case in your snippet does not look like an actual need nowadays, at least not to me. (no offence)

Thank you for your issue anyway!