Inheritance with Lo-Dash

Question

I am trying to emulate inheritance in javascript using a the Lo-Dash javascript library.

I am simply using _.extend to do so:

function Parent() {
  var self = this;

  self.hello = function () {
    console.log('Hello from parent');
  };
}

function Child() {
  var self = this;

  _.extend(self, Parent);
}

Child.hello(); // Doesn't exist

I thought this would work since all javascript functions are objects but obviously I am wrong. Why doesn't this work and how would I properly emulate inheritance using Lo-Dash?

That happens because function `Child` doesn't have `hello` property. See [How to “properly” create a custom object in JavaScript?](http://stackoverflow.com/a/1598077/251311) — zerkms, Aug 05 '14 at 23:05
Even if you did it correctly you would not really inherit but just copy members of one onto another (more like mix in) for a detailed answer about JavaScript inheritance you can view this answer. http://stackoverflow.com/questions/16063394/prototypical-inheritance-writing-up/16063711#16063711 — HMR, Aug 06 '14 at 07:04

score 13 · Answer 1 · answered Oct 02 '14 at 21:05

13

See _.create documentation for a working example.

answered Oct 02 '14 at 21:05

pmark

281
2
9

1

This best answers the question because it is what the method was designed for - https://github.com/lodash/lodash/issues/663 – cchamberlain Apr 16 '15 at 06:19
1

this is a link-only answer – JBCP May 13 '16 at 19:02

score 6 · Accepted Answer · answered Aug 06 '14 at 00:09

Parent is simply the constructor for the Parent class, it does not itself have the hello property that it adds to self. You could just change the _.extend line to this: _.extend(self, new Parent()) to solve it. This works because the object returned by new Parent() does have a hello property that _.extend can copy over to self.

To access the hello property you will also have to create an instance of the Child class rather than accessing hello on the constructor. After making the above change, (new Child()).hello() should work because you accessing the hello property on the Child instance not the constructor.

But, this seems to me to be a poor solution because new Child() instanceof Parent will return false. If you want to properly set up the prototype chain so there is "true" inheritance going on you should read about psuedoclassical and prototypal inheritance.

score 4 · Answer 3 · answered Mar 09 '17 at 11:59

You could use _.create() function and prototype to emulate inheritance.

function Parent() {}

Parent.prototype.hello = function() {
    console.log('Hello from parent');
};

function Child() {}

Child.prototype = _.create(Parent.prototype, {
    'constructor': Child
});

var child = new Child();
child.hello(); //Hello from parent

Inheritance with Lo-Dash

3 Answers3

Linked