Harvey Triana's Blog

JavaScript reactivity with custom events

Without design patterns we can add native reactivity with custom events

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Harvey Triana
·

1 min read

In this short example I show how from a custom event we can inadvertently send messages to the browser from the same application. I use the object paradigm in JavaScript here. Simple and efficient.

JavaScript Object sample,

/* 
CUSTOM EVENTS
File: drunk_events.js
*/
var eventArgs = {
    message: ''
};
const drunkMessagesEvent = new CustomEvent("drunkMessages", {
    detail: eventArgs
});
// CLASS
class Drunk extends Event {
    constructor(name, limit) {
        super('drunkMessages');
        this.name = name;
        this.limit = limit;
    }

    Drink() {
        const name = this.name;
        const limit = this.limit;
        const task = setInterval(timingTask, 1000);
        var count = 0;

        function timingTask() {
            count++;
            if (count > limit) {
                eventArgs.message = name + ' go to sleep';
                // stop timing task
                clearInterval(task);
            } else {
                eventArgs.message = 'Drinking ' + count + ' of ' + limit;
            }
            document.dispatchEvent(drunkMessagesEvent);
        }
    }
}

UI sample, index.html file:

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <h1>Drunk</h1>
    <div id="prompt"></div>
</body>

<script src="drunk_events.js"></script>
<script>
    // testing
    prompt = document.getElementById('prompt');

    const drunk = new Drunk('Alice Cooper', 12);
    drunk.Drink();

    document.addEventListener("drunkMessages", e => {
        prompt.textContent = e.detail.message;
    });
</script>

</html>
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