How to make fadeOut effect with pure JavaScript

Question

I\'m trying to make fadeOut effect for a div with pure JavaScript.

This is what I\'m currently using:

//Imagin         


        

Answer 1

Initially when there's no opacity set, the value will be an empty string, which will cause your arithmetic to fail. That is, "" < 0.1 == true and your code goes into the clearInterval branch.

You can default it to 1 and it will work.

function fadeOutEffect() {
    var fadeTarget = document.getElementById("target");
    var fadeEffect = setInterval(function () {
        if (!fadeTarget.style.opacity) {
            fadeTarget.style.opacity = 1;
        }
        if (fadeTarget.style.opacity > 0) {
            fadeTarget.style.opacity -= 0.1;
        } else {
            clearInterval(fadeEffect);
        }
    }, 200);
}

document.getElementById("target").addEventListener('click', fadeOutEffect);

#target {
    height: 100px;
    background-color: red;
}

Click to fade

An empty string seems like it's treated as a 0 by JavaScript when doing arithmetic and comparisons (even though in CSS it treats that empty string as full opacity)

> '' < 0.1
> true

> '' > 0.1
> false


> '' - 0.1
> -0.1

Simpler Approach We can now use CSS transitions to make the fade out happen with a lot less code

const target = document.getElementById("target");

target.addEventListener('click', () => target.style.opacity = '0');
// If you want to remove it from the page after the fadeout
target.addEventListener('transitionend', () => target.remove());

#target {
    height: 100px;
    background-color: red;
    transition: opacity 1s;
}

Some text before

Click to fade
Some text after