Referenceerror: event is not defined error in Firefox

javascript

event-handling

jquery

best-practices

byNikita Barsukov·Jan 2, 2025

Fix the ReferenceError: event is not defined by explicitly passing the event object as a parameter in your event handler:

element.addEventListener('type', function(e) {
    // Use 'e' for event actions
    // Yes, it's as simple as adding e here. No magic!
    console.log(e.target);
});

Even if some browsers seem to allow forgetting the event parameter, including it is a matter of best practice to ensure full compatibility.

Event parameters and their significance

In the world of JavaScript event handling, passing an event object explicitly means the dish is being served with the right ingredients. It's as if you are the master chef and the event object is the special sauce.

Event parameters in jQuery and their traits

When using jQuery, there's a unique standardization across browsers when working with events. So, using event as a parameter in your event handlers within jQuery means consistency across browsers.

$('.button').on('click', function(e) {
    // e here is the secret ingredient. It makes things taste right!
});

Why using identifiers matters

The practice of passing an argument to a function and giving it a name, such as event or e, plays a vital role in maintaining consistency and clarity in your code.

Remember, a great function call is much like a great cupcake recipe -- an ingredient with a name is as important as the ingredient itself.

$('a').click(function(e) { 
    // Welcome e to the party!
});

Access trigger element actions

You can easily access the triggering element with either 'e.currentTarget' or $(this). To prevent the default action in browser events, use the 'e.preventDefault()' method in jQuery. This is particularly handy in dealing with clicks on links or buttons when you want to design the exact flow of user experience.

$('a').on('click', function(e) {
    e.preventDefault(); 
    // Every party has some ground rules. Here's ours.
    var sectionToShow = $(this).attr('rel');
    // Use the 'rel' attribute like the map leading to the hidden treasure. 
    $('section').hide().filter(sectionToShow).fadeIn();
});

Best practices for passing event objects

Event object is your ticket to the event

When we ensure to explicitly pass the event object to the function, we are setting up our base camp right, avoiding unnecessary browser compatibility issues like a seasoned trekker avoids landslides.

document.querySelector('.menuOption').addEventListener('click', function(e) {
    // Your e-ticket to the event.
});

The game of names

In the tournament of jQuery naming conventions, you are the champion. The name of the event parameter carries the weight in the world of coding but it's all in your power whether you choose e or evt or cupcake.

$('.menuOption').on('click', function(cupcake) {
    // Because why not?
});

Relying on jQuery standardization

jQuery's event object is a protective shield around the native event object, providing you the strength of consistency across a variety of browsers. Utilize this to the fullest, coding kinsfolk!

$(document).on('keydown', function(e) {
    if(e.which === 13) { 
        console.log('Enter was pressed');
        // Or as we call it, the "keyboard high-five"!
    }
});

Common troubles and fixes in event handling

Pandemic known as 'ReferenceError'

The ReferenceError: event is not defined error is a common hiccup while migrating from other browsers to Firefox. Avoiding this misstep is made easy by explicit passing of event object, even when other browsers seem lenient.

The pitfalls of event object negligence

Insufficient attention to passing the event object properly may steer us to an unexpected off-track ride of errors and inconsistencies. But, fear not! A simple fix of passing the provided event parameter to your function saves the day.

decoding 'this' vs. event.currentTarget

The confusion between this and event.currentTarget within event handlers is understandable. But, keep in mind always to use event.currentTarget for utmost clarity and reliability.

document.querySelector('.menuOption').addEventListener('click', function(e) {
    console.log(this); // Under the spotlight now!
    console.log(e.currentTarget); // Who's there? It's me, the event doer!
});