Consider not filtering out properties that are explicitely set to undefined

There are use-cases in which it makes sense to set a property to undefined and still expect it to be copied. Object.assign() does not filter out such properties, either.

What’s the reason for them to be filtered in node-extend?

[danielo515]

However, this module is exclusively to mirror jQuery’s “extend” function, so that’s the behavior it will preserve.

I recommend https://npmjs.com/object.assign if you want an official polyfill for the native language feature.

That exact advice is what I expect to be more noticeable. Since this module is just called extend, it could lead to confusion. I know that the very first sentence is that it mirrors JQuery’s extend function, but for people who is not familiar with JQuery it means nothing. A small explanation of the unexpected behaviors would be nice, and of course your recommendation for another polyfill

Thanks and regards

[ljharb]

Ah, I understand what this issue is about now.

Object.assign does do what you mean - in other words, Object.assign({}, { value: 3 }, { value: undefined }) will result in { value: undefined }.

However, this module is exclusively to mirror jQuery’s “extend” function, so that’s the behavior it will preserve.

I recommend https://npmjs.com/object.assign if you want an official polyfill for the native language feature.