Notes
In Lightning Web Components (LWC), there is often a need to dynamically assign CSS classes to elements based on the state of the component. In earlier approaches, developers used JavaScript string concatenation or template literals to manipulate the class attribute. However, modern LWC approaches allow you to handle dynamic class assignment in a cleaner and more declarative way by using getter functions.
In this article, we will explore how to dynamically generate classes and assign them to a specific HTML element using a different approach in LWC.
Example Scenario: Adding Styles Based on User Interaction
Let’s imagine that we are creating a button in LWC that can toggle between "active" and "inactive" states. Based on the state, we want to change the button's appearance using CSS classes.
HTML
<template>
<button class={computedClassNames} onclick={toggleActiveState}>
{label}
</button>
</template>
JavaScript
import { LightningElement } from 'lwc';
export default class ToggleButton extends LightningElement {
isActive = false;
get label() {
return this.isActive ? 'Active' : 'Inactive';
}
get computedClassNames() {
return this.isActive ? 'button-active' : 'button-inactive';
}
toggleActiveState() {
this.isActive = !this.isActive;
}
}
CSS
button {
padding: 10px 20px;
font-size: 16px;
cursor: pointer;
}
.button-active {
background-color: green;
color: white;
}
.button-inactive {
background-color: red;
color: white;
}
How It Works
- When the component is rendered, the button will have the
button-inactive class by default.
- When the user clicks the button, the
toggleActiveState() method toggles the value of isActive, which in turn updates the computedClassNames getter.
- The button's class changes dynamically, and the new styles are applied.
Conclusion
By using the power of getter methods in LWC, we can easily compute and assign CSS classes dynamically based on the component's state. This approach simplifies the process of managing class names and keeps our code clean and maintainable. Instead of relying on string concatenation, we let the getter handle the logic, making the code easier to read and extend.
This pattern can be applied in various scenarios, such as adding conditional styling based on user interactions, displaying dynamic content, or toggling features on and off.
