Table of contents

Destructuring with default values in Javascript

Destructuring with default values in Javascript

In the previous post I briefly discussed the topic of destructuring with nested objects in javascript . In this post I am going to talk a bit about how we can specify default values when destructuring an object in javascript.

To do this we will create a fairly simple object:

const user = {
  userIsLoggedIn: true, 
  email: "[email protected]",
  accountType: "premium" 
}

This object could be the response to an API request. From the previous object we could destructure three properties, userIsLoggedIn, email and accountType.

const { userIsLoggedIn, email, accountType } = user

But, what would happen if there is a change in the API and now it no longer returns the accountType property, this would be enough for all the part of the frontend that depends on the presence of that variable to have errors.

if(accountType==='Admin'){
  showAdvancedMenu()
}
if(accountType==='basic'){
  showBasicMenu()
}

Well, to avoid this we can assign a default value when the destructuring does not find the property that we want to destructure. If you are following this example remember to clean the javascript terminal and re-declare the main object or you will get an error.

Assigning a default value when destructuring an object in Javascript

This time let’s declare the user object without the accountType property:

const user = {
  userIsLoggedIn: true, 
  email: "[email protected]"
}

Well, if we try to destructure the object and assign a default value if the appropriate property is not found we will do it in the following way:

const { userIsLoggedIn, email, accountType="basic" } = user
accountType
"basic"

The accountType constant returns ‘basic’, a property that the original object lacked, but will now have a default value if omitted. This allows us to keep the frontend without major changes to a modified HTTP response and to handle the absence of some property in an object.

I know that sometimes this topic can be quite difficult, I also had a hard time understanding it the first time, the destructuring makes the already confusing Javascript code much more readable. If you still find Javascript confusing I leave you a post where I talk about what I consider the best book to learn Javascript at intermediate level.

Eduardo Zepeda
Web developer and GNU/Linux enthusiast always learning something new. I believe in choosing the right tool for the job and that simplicity is the ultimate sophistication. I'm under the impression that being perfect is the enemy of getting things done. I also believe in the goodnesses of cryptocurrencies outside of monetary speculation.
Read more