How Can Event Delegation Improve Vanilla JavaScript Performance and Code Simplicity?

Event Delegation with Vanilla JavaScript

In vanilla JavaScript, event delegation is a technique used to attach event listeners to a single parent element instead of individual elements within it. This approach improves performance by eliminating the need for multiple event listeners and simplifies the code.

Effective Event Delegation

To implement event delegation efficiently, use the following steps:

1. Find the parent element where the events will occur.
2. Add an event listener to the parent element for the desired event type (e.g., click).
3. Inside the event handler, check if the clicked element matches a specific selector or its parent elements match the selector.
4. If the condition is met, execute the desired function or action.

Example: Delegating jQuery Code

Consider the following jQuery code:

$('#main').on('click', '.focused', function() {
    settingsPanel();
});

To translate this code to vanilla JavaScript, use the following:

document.querySelector('#main').addEventListener('click', (e) => {
    if (e.target.closest('.focused')) {
        settingsPanel();
    }
});

In this code, we use querySelector() to find the parent element with the ID main and attach a click event listener to it. When an element within this parent is clicked, it checks if the clicked element or any of its parent elements have the .focused class. If so, it invokes the settingsPanel() function.

Benefits of Delegating:

• Improved performance: Eliminates the need for multiple event listeners, reducing the number of event handling functions.
• Simplified code: Easier to maintain and understand compared to using individual event listeners for each element.
• Flexibility: Allows for dynamic binding of event handlers based on selectors, enabling you to handle events from elements that may be added or removed dynamically.

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