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JavaScript

Angelic Sanoy
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Angelic Sanoy
Full Stack JavaScript Techdegree Student 6,580 Points

What's the difference between event handler and html event?

I just noticed that sometimes an event is wrap into html like which I assume this is called html event.

<button onclick="document.getElementById('demo').innerHTML = Date()">The time is?</button>

While others are wrap in Javascript like below: btn.addEventListener('click', () => { const rndCol = rgb(${random(255)}, ${random(255)}, ${random(255)}); document.body.style.backgroundColor = rndCol; });

Wondering when I should use the event handler and html event. Also, does the event handler always accompanied with event listener?

1 Answer

Steven Parker
Steven Parker
230,248 Points

In both cases, an event listener is being established along with a handler function to run when the event occurs. The listener is implied when setting the handler using the HTML properties.

However, it is considered "best practice" to establish listeners using JavaScript code., and that method also provides additional functionality. Setting handlers with HTML properties is typically used only for testing or in trivial programs which otherwise have no JavaScript component.

Angelic Sanoy
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Angelic Sanoy
Full Stack JavaScript Techdegree Student 6,580 Points

Thank you Steve, your answer is on point. So in short, if we compare this into HTML/CSS. HTML event is like an inline style while event handler is the css.

Steven Parker
Steven Parker
230,248 Points

Close, setting a handler by assigning an "on___" HTML property could be considered an "inline" method, but there really isn't any CSS component to a handler. It's all JavaScript.