Best practice to extend objects in underscore.js

javascript underscore.js extend relation
Sebastian picture Sebastian · Mar 8, 2015 · Viewed 16.1k times · Source

I know that extending objects is done via the 

_.extend(parent, child);

method.

I've seen different places in the web where people are extending objects in a special way in underscore.js

_.extend({}, this, child);

Why do they do that?

Answer

syed imty picture syed imty · Mar 8, 2015

According to the underscore documentation, The api of _.extend method is 

_.extend(destination, *sources)

First Sample

_.extend(parent, child);

In this sample code, you are actually extending the properties from child object to parent object. Here the parent object is modified.

Second Sample

_.extend({}, parent, child);

In case you don't want to modify the parent object, and still want both the properties from parent and child. You can use this one. Here you are extending parent object, and child object to a new object.

Related questions

Most efficient method to groupby on an array of objects

What is the most efficient way to groupby objects in an array? For example, given this array of objects: [ { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" }, { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" }, { …

Read More
Differences between Lodash and Underscore.js

Why would someone prefer either the Lodash or Underscore.js utility library over the other? Lodash seems to be a drop-in replacement for underscore, the latter having been around longer. I think both are brilliant, but I do not know …

Read More
How to use underscore.js as a template engine?

I'm trying to learn about new usages of javascript as a serverside language and as a functional language. Few days ago I heard about node.js and express framework. Then I saw about underscore.js as a set of utility …

Read More