This article covers creating a Riot Switch component, using the Material Design CSS BeerCSS. Before starting, make sure you have a base application running, or read my previous article Setup Riot + BeerCSS + Vite.

These articles form a series focusing on RiotJS paired with BeerCSS, designed to guide you through creating components and mastering best practices for building production-ready applications. I assume you have a foundational understanding of Riot; however, feel free to refer to the documentation if needed: https://riot.js.org/documentation/

Four Switch states exist: checked, unchecked, disabled, and mixed (see the following screenshot). The goal is to create a switch Riot component with BeerCSS design and listen to change events.

Switch Component Base

First, create a new file named c-switch.riot under the components folder. The c- stands for "component", a useful naming convention and a good practice.

Into ./components/c-switch.riot, write the following HTML (found on the BeerCSS documentation):

<c-switch>
    <label class="
            switch
            { props?.icon ? 'icon' : ''}
        ">
        <input type="checkbox" value={ props?.value ? true : false  } checked={ props?.value } disabled={ props?.disabled }>
        <span>
            <i if={ props?.icon }>{ props.icon }</i>
        </span>
    </label>
</c-switch>

Let's break down the code:

• The <c-switch> and </c-switch> defined a custom root tag, with the same name as the file. You must write it; otherwise, it may create unexpected results. Using the <label> as a root tag or redefining native HTML tags is a bad practice, so starting c- is a good naming.
• To enable the checked attribute, the props.value must exist and be true.
• Behind the switch, it uses an input tag as a checkbox, and the value and checked are two different attributes; the component unifies the input and checked values.
• The element is disabled if the props.disabled attribute exists and the value is true.
• A custom icon can be displayed on the switch; the props.icon HTML attribute must exist and it will add a class icon and a tag <i>icon_name</i>.

Finally, instantiate the c-switch.riot into a front page index.riot:

<index-riot>
    <div style="width:600px;padding:20px;">
        <h4 style="margin-bottom:20px">Riot + BeerCSS</h4>
        <c-switch  onclick={ clicked } value={ state.value } /><br>
        <c-switch icon="wifi" value={ true } /><br>
        <c-switch icon="bluetooth" disabled={ true } /><br>
        <c-switch icon="dark_mode" disabled={ true } value={ true} /><br>
    </div>
    <script>
        import cSwitch from "./components/c-switch.riot";

        export default {
            components: {
                cSwitch
            },
            state: {
                value: true
            },
            clicked (ev) {
                if (ev.target.tagName === "INPUT") {
                    this.update({ value: !this.state.value })
                }
            }
        }
    </script>
</index-riot>

Code break-down:

1. The component is imported with import cSwitch from "./components/c-switch.riot"; then loaded into the components:{} Riot object.
2. The component is instantiated with <c-switch /> on the HTML. Add the attribute "icon" to display a Google Material Icon, such as <c-switch icon="home" />
3. The state of the switch is stored in the state Riot object state: { value: true }. True is the default value.
4. To listen to a click or change event, the attribute onclick={} or onchange={} must be bound to a local function. In our case, it is firing the clicked function.
5. On click, the state.value is updated to its opposite with this.update({ value: !this.state.value }).
6. An important issue occurs: the event click is emitted twice! The expression if (ev.target.tagName === "INPUT") accepts only one event.

Screenshot of the generated HTML:

Fix the Switch issue: stop the double-click event

As mentioned in the previous section, the click event is fired twice. The issue is that clicking the label triggers a click on both the <c-switch> tag and the child switch input <input type="checkbox">.

The solution is to stop the event propagation inside the component and re-emit the event once. During this moment, I take the opportunity to change the Boolean value to its opposite: the parent HTML will receive a change event with the correct value:

• the change event emits true if the input is checked.
• the change event emits false if the input is unchecked.

The c-switch.riot updated:

<c-switch>
    <label 
        class="
            switch
            { props?.icon ? 'icon' : ''}
        " 
        onclick={ clicked }
    >
        <input type="checkbox" value={ props?.value ? true : false  } checked={ props?.value } disabled={ props?.disabled }>
        <span>
            <i if={ props?.icon }>{ props.icon }</i>
        </span>
    </label>
    <script>
        export default {
            clicked (e) {
                e.preventDefault();
                e.stopPropagation();
                this.root.value = this.props.value === true || this.props.value === "true" ? false : true;
                this.root.dispatchEvent(new Event('click'));
                this.root.dispatchEvent(new Event('change'));
            }
        }
    </script>
</c-switch>

Code breakdown:

• If a click occurs on the <label>, the click event is not propagated and cancelled, thanks to e.preventDefault(); and e.stopPropagation();
• The value of the switch input takes its opposite.
• The click and change events are re-emitted thanks to the dispatchEvent

The update of the state.valueon the parent component index.riot can be simplified:

<index-riot>
    <div style="width:600px;padding:20px;">
        <h4 style="margin-bottom:20px">Riot + BeerCSS</h4>
        <c-switch  changed={ changed } value={ state.value } /><br>
    </div>
    <script>
        import cSwitch from "./components/c-switch.riot";

        export default {
            components: {
                cSwitch
            },
            state: {
                value: true
            },
            changed (ev) {
                this.update({ value: ev.target.value })
            }
        }
    </script>
</index-riot>

Now the state.value takes the value from the change Event, and the Event value always mirrors the current state of the switch. Most of all: the click event is fired only one time.

Tips to simplify even more: It is not required to create a "changed" function, one line is enough to update the value:

<c-switch  changed={ (ev) => update({ value: ev.target.value }) } value={ state.value } /><br>

Switch Component Testing

It exists two methods for testing the Switch component, and it is covered in two different articles:

• Test with Vitest and Riot-SSR in a Node Environment
• Test with Vitest in a JsDom Environment

Conclusion

Voilà 🎉 We created a Switch Riot Component using Material Design elements with BeerCSS.

The source code of the switch is available on Github:
https://github.com/steevepay/riot-beercss/blob/main/components/c-switch.riot

Feel free to comment if you have questions or need help about RiotJS.

Have a great day! Cheers 🍻