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Discover how to efficiently replace the last digit of a CSS class in JavaScript without declaring an external variable. This guide simplifies the process using the power of template literals and classList methods.
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This video is based on the question https://stackoverflow.com/q/77184003/ asked by the user 'Mnda' ( https://stackoverflow.com/u/22641069/ ) and on the answer https://stackoverflow.com/a/77184031/ provided by the user 'Patrick Evans' ( https://stackoverflow.com/u/560593/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Replace a Class Name Dynamically in JavaScript Without External Variable

In web development, there are often situations where you need to modify class names dynamically, especially when working with animations or providing a random effect. A common problem that developers encounter is needing to update a class that ends with a number, replacing it with a randomly generated number—without declaring an external variable. If you have faced this challenge, you're certainly not alone! Here, we'll break down a straightforward solution that utilizes JavaScript effectively.

The Problem

Imagine you have a function that should update the class of an element .home by changing the number at the end of the class name home--X, where X is a digit between 0 and 9. Originally, you might have implemented this by declaring a variable outside of the function. While this works, it's not an elegant solution since it leaves the global scope cluttered.

You could have a solution where, upon calling this function, the digit is chosen randomly without needing the variable across multiple calls. This leads to a cleaner codebase and better encapsulation of variables and functionality.

The Solution

Using Template Literals and Random Number Generation

JavaScript's template literals, marked by backticks (`), allow us to embed arbitrary JavaScript expressions directly within a string. We can leverage this feature to simplify our function.

Here’s how you can do it:

Select the Element:
First, you need to select the element whose class you're going to modify.

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

Add a New Class with a Random Number:
Using gsap.utils.random(0, 9, 1) to generate a random number, you can add a new class directly:

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

Alternatively, for traditional string concatenation, you can do:

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

Removing the Existing Class

Since the goal is to replace the class ending in a number, you need to first remove the existing class. To efficiently do this without needing an external variable, you can loop through the list of classes:

Here’s an effective way to remove the old class:

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

Complete Implementation

Here's how your complete function might look when all pieces come together:

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

Conclusion

By using template literals and the classList property effectively, you can manage class names dynamically without declaring unnecessary external variables. This not only keeps your code cleaner but also enhances maintainability. So next time you find yourself needing to update classes based on randomness, remember these clean techniques! Happy coding!