<div class="box green"></div>
<div class="box orange"></div>
<div class="box grey"></div>

/* Global styles come from external css https://codepen.io/GreenSock/pen/JGaKdQ*/

body {
  margin-top: 50px;
  text-align: center;
}

.box {
  display: inline-block;
  margin-right: 5px;
}

.pink {
  background-color: pink;
}

// register the effect with GSAP:
gsap.registerEffect({
    name: "fade",
    defaults: {duration:2}, //defaults get applied to the "config" object passed to the effect below
    effect: (targets, config) => {
        return gsap.to(targets, {duration: config.duration, opacity:0});
    }
});

// now we can use it like this:
gsap.effects.fade(".green");

// Wait a bit and override the defaults:
gsap.delayedCall(3, () => gsap.effects.fade(".orange", {duration: 1}) );

document.querySelector(".grey").addEventListener("mouseenter", e => gsap.effects.fade(e.target));