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HTML

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Adding Classes

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About the <head>

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Insecure Resource

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CSS

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CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

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JavaScript

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JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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HTML 

              
                <header class="header header--inverted"> Header </header>
<header class="header header--normal"> Header </header>

<div class="page">  
  <section class="section">A</section>
  <section class="section section--dark">
    B
  </section>
  <section class="section">
    C
    <button onclick="makeLarger()">Make red box higher</button>
    <div class="red">RED BOX</div>
  </section>
  <section class="section section--dark">
    D
  </section>
</div>
!

CSS 

              
                @import url('https://fonts.googleapis.com/css?family=Signika+Negative:300,400&display=swap');

body {
  padding: 0;
  margin: 0;
  height: 1000px;
}

.page {
  position: relative;
  padding-top: 56px;
}

.header {
  position: fixed;
  font-size: 16px;
  padding: 20px;
  background: white;
  color: black;
  width: 100%;
  z-index: 1000;
} 

.header--inverted {
  background: black;
  color: white;
}

.section {
  min-height: 300px;
  padding: 30px;
}

.section--dark {
  background: black;
  color: white;
}

.red {
  background: red;
  width: 200px;
  height: 100px;
  color: white;
}
!

JS 

              
                gsap.registerPlugin(ScrollTrigger);
gsap.config({ trialWarn: false });
console.clear();

const normalNavbar = document.querySelector(".header--normal");
const invertedNavbar = document.querySelector(".header--inverted");
const darkSections = document.querySelectorAll(".section--dark");

const setEffect = () => {
  const timeline = gsap.timeline();

  timeline.set(normalNavbar, {clipPath: 'inset(0px 0 0px 0)'});
  timeline.set(invertedNavbar, {clipPath: `inset(${ invertedNavbar.offsetHeight }px 0 0px 0)`});

  darkSections.forEach((section, index) => {
      //inverted navbar
      timeline.fromTo(invertedNavbar, {
          clipPath: 'inset(0px 0 0px 0)',
          immediateRender: false
      }, {
          scrollTrigger: {
              trigger: section,
              start: () => `bottom ${ invertedNavbar.offsetHeight }px`,
              id: `navbar-from-dark${ index }`,
              end: () => `+=${ invertedNavbar.offsetHeight }px`,
              scrub: true,
              invalidateOnRefresh: true,
              // for debugging purposes set to true
              markers: true
          },
          clipPath: `inset(0px 0 ${ invertedNavbar.offsetHeight }px 0)`,
          ease: 'none'
      });

      timeline.fromTo(invertedNavbar, {
          clipPath: `inset(${ invertedNavbar.offsetHeight }px 0 0px 0)`,
          immediateRender: false
      }, {
          scrollTrigger: {
              trigger: section,
              start: () => `top ${ invertedNavbar.offsetHeight }px`,
              end: () => `+=${ Math.ceil(invertedNavbar.offsetHeight)}px`,
              id: `navbar-from-white${ index }`,
              scrub: true,
              invalidateOnRefresh: true,
              // for debugging purposes set to true
              markers: true
          },
          clipPath: 'inset(0px 0 0px 0)',
          ease: 'none'
      });

      // normal navbar
      timeline.fromTo(normalNavbar, {
          clipPath: `inset(${ normalNavbar.offsetHeight }px 0 0px 0)`,
          immediateRender: false
      }, {
          scrollTrigger: {
              trigger: section,
              start: () => `bottom ${ normalNavbar.offsetHeight }px`,
              id: `navbar-normal-from-dark${ index }`,
              end: () => `+=${ normalNavbar.offsetHeight }px`,
              scrub: true,
              invalidateOnRefresh: true,
              // for debugging purposes set to true
              markers: true
          },
          clipPath: 'inset(0px 0 0px 0)',
          ease: 'none'
      });

      timeline.fromTo(normalNavbar, {
          immediateRender: false,
          clipPath: 'inset(0px 0 0px 0)',
      }, {
          scrollTrigger: {
              trigger: section,
              start: () => `top ${ normalNavbar.offsetHeight }px`,
              end: () => `+=${ Math.ceil(normalNavbar.offsetHeight)}px`,
              id: `navbar-normal-from-white${ index }`,
              scrub: true,
              invalidateOnRefresh: true,
              // for debugging purposes set to true
              markers: true
          },
          clipPath: `inset(0px 0 ${ normalNavbar.offsetHeight }px 0)`,
          ease: 'none'
      });
  });
}

const makeLarger = () => {
  const redBox = document.querySelector(".red");
  redBox.style.height = "800px";
}

const killScrollTriggers = () => {
			const allTriggers = ScrollTrigger.getAll();
			allTriggers.forEach((trigger) => {
				if (trigger.trigger.classList.contains('section--dark')) {
					trigger.kill(true);
				}
			});
  
      console.log(ScrollTrigger.getAll(), "killed?");
}

const setDocumentHeightObserver = () => {
			const body = document.querySelector('body');

			const observer = new ResizeObserver(() => {
        console.log("height changed");
        ScrollTrigger.refresh()
        //killScrollTriggers();
				//setEffect();
			});

			for (let i = 0; i < body.children.length; i++) {
				observer.observe(body.children[i]);
			}
}

setEffect();
setDocumentHeightObserver();
!
999px

Console