Скачать или смотреть Mastering the ng-repeat Directive: Using the Ternary Operator in AngularJS

Discover how to effectively use the `ng-repeat` directive in AngularJS with conditional lists using the ternary operator. Learn to streamline your code for better readability and performance.
---
This video is based on the question https://stackoverflow.com/q/63832452/ asked by the user 'CyborgNinja23' ( https://stackoverflow.com/u/4815994/ ) and on the answer https://stackoverflow.com/a/63832512/ provided by the user 'Petr Averyanov' ( https://stackoverflow.com/u/4019404/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Using Ternary Operator Inside ng-repeat Directive

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Using the Ternary Operator Inside ng-repeat Directive in AngularJS

When working with AngularJS, one common requirement is to conditionally display lists based on certain variables or flags. A frequent question arises: Can I use a ternary operator within the ng-repeat directive? The short answer is no, but there’s a straightforward workaround that can help you achieve the desired functionality seamlessly.

Understanding the Problem

The ng-repeat directive is a powerful tool in AngularJS that allows you to iterate over collections and render them in your views. You might find yourself in a scenario where you need to switch between different lists based on a certain condition or flag. For example, let's say you want to display either a dark theme list or a normal theme list, depending on the user's preference for dark mode.

Example Use Case

Given a variable $ctrl.darkMode that holds a boolean value:

If $ctrl.darkMode is true, you want to display the darkList.

If $ctrl.darkMode is false, you want to display the normalList.

A naive approach might look something like this:

[[See Video to Reveal this Text or Code Snippet]]

But this will not work as intended. Let’s dive into the solution that you can employ instead.

The Solution

Instead of attempting to implement the ternary operator directly within the ng-repeat, you can restructure your code to maintain clarity and functionality. Here’s how:

Recommended Approach

Use the ternary operator outside the ng-repeat as part of the expression evaluating the list to iterate over:

[[See Video to Reveal this Text or Code Snippet]]

This approach ensures that the condition is evaluated correctly, and ng-repeat iterates over the appropriate list based on the flag.

When Conditions Get Complex

In cases where you find yourself dealing with more complicated conditions, it’s a good practice to extract the logic into a function that returns the desired list. This keeps your templates clean and maintains readability. For example:

Define the function in your controller:

[[See Video to Reveal this Text or Code Snippet]]

Use the function in your ng-repeat:

[[See Video to Reveal this Text or Code Snippet]]

This approach is not only cleaner but also allows you to encapsulate logic within your controller, making your view much easier to manage.

Final Thoughts

Understanding how to effectively use the ng-repeat directive combined with the ternary operator is essential for creating dynamic and responsive AngularJS applications. By adopting the correct practices outlined above, you can ensure that your code is not only functional but also maintainable and easily readable. Remember to extract complex logic to controller functions whenever necessary, keeping your views tidy and straightforward.

By mastering these techniques, you're well on your way to becoming proficient in AngularJS and enhancing the interactivity of your web applications.