Web Assembly (Wasm) is a low-level bytecode format designed to run in modern web browsers. With Wasm, we can write performant code in languages such as C, C++, and Rust, and run them directly in the browser. To interact with Web Assembly modules from JavaScript, we often need to listen for events and respond to them accordingly.

In this blog post, we will explore how to set up event listeners for Web Assembly events in JavaScript.

Adding an Event Listener

To add an event listener for a Web Assembly event, we first need to retrieve the DOM element that will fire the event. Then we can use the addEventListener method to attach a listener function to the event.

const wasmElement = document.getElementById('wasmModule');  // Replace 'wasmModule' with the actual ID of your Wasm module element

wasmElement.addEventListener('event_name', event => {
    // Handle the event
});

Make sure to replace 'event_name' with the actual name of the event you want to listen for. For example, if you want to listen for a click event on a Web Assembly button, you can use 'click' as the event name.

Handling the Event

Inside the event listener function, you can write the code to handle the event. This can include calling functions from the Web Assembly module or manipulating the DOM based on the event.

wasmElement.addEventListener('click', event => {
    // Call a function from the Web Assembly module
    wasmModule.exports.handleButtonClick();

    // Manipulate the DOM
    event.target.style.backgroundColor = 'blue';
});

In this example, we call a function called handleButtonClick() from the Web Assembly module when the button is clicked. Additionally, we change the background color of the clicked element to blue.

Removing an Event Listener

To remove an event listener, we can use the removeEventListener method. This requires both the event name and the listener function used to attach the listener.

const listenerFunction = event => {
    // Listener function code
};

wasmElement.addEventListener('click', listenerFunction);

// Remove the event listener
wasmElement.removeEventListener('click', listenerFunction);

In this code snippet, we attach an event listener using the listener function listenerFunction. Then we remove the event listener using the same event name and listener function.

Conclusion

With Web Assembly becoming more prevalent in web development, it is important to understand how to listen for events and handle them in JavaScript. By following the steps outlined in this blog post, you should now have a good understanding of how to add event listeners, handle events, and remove event listeners for Web Assembly events in JavaScript.

#webassembly #javascript