Hey, I've encountered this need a lot, and lately, I've been toying with the idea of opening a PR about it. But before I do, I want to make sure there really isn't a way of doing what I need using pure Lodash.

Case 1

Functionally add/set a field to an object. We expand on this in case 2.

// Before_({name:'Tomer',age:23})// After_({name:'Tomer'}).extend({age:23})// Creates a new object and doesn't modify the original in-place.// {name: 'Tomer', age: 23}

Case 2

Expanding on case 1, functionally add/set a field based on the object's current values:

// Beforeconstbirthday=moment('10/04/2001');_({name:'Tomer',   birthday,age:birthday.diff(moment(),'years')})// After_({name:'Tomer',birthday:moment('10/04/2001')}).extend(obj=>({age:obj.birthday.diff(moment(),'years')}))// {name: 'Tomer', birthday: <moment>, age: 23}

Case 3

Expanding on case 2, applying the extend function to each object in an array:

_(people).extend(obj=>({age:obj.birthday.diff(moment(),'years')}))// Applies the previously mentioned `extend` to each of the objects in the list// Basically .map(.extend())

I know there's an existingextend function that modifies the target object in place instead of creating a new object. It also doesn't support dynamic assignment (case 2) or an array equivalent (case 3).

If I would proceed with creating a PR, maybe adding a differently named function will be more fitting.