<body>
  <div class="main-content">
    main content
    <trigger-modal name="my-modal">
      <label>
        open modal
        <input type="checkbox" role="button" form="modal-form-my-modal">
      </label>
    </trigger-modal>
  </div>

  <dialog-modal name="my-modal" main-content-class="main-content">
    <div id="modal-container-my-modal">
      <button class="modal-overlay" tabindex="-1" form="modal-form-my-modal" type="reset"></button>
      <div class="modal-body" role="dialog">
        <button tabindex="-1" form="modal-form-my-modal" type="reset">x</button>
        Dialog 1
        <close-modal name="my-modal">
          <button type="reset" form="modal-form-my-modal">
            Close Modal
          </button>
        </close-modal>
      </div>
      <form id="modal-form-my-modal"></form>
    </div>

  </dialog-modal>

</body>
trigger-modal label > input {
  opacity: 0;
  position: absolute;
  height: 1px;
  width: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
}

trigger-modal label {
  border: 1px solid black;
  border-radius: 3px;
  font-style: san-serif;
  padding: 2px 5px;
}

trigger-modal label:focus-within {
  outline: 1px dashed red;
}

body {
  position: relative;
}

.main-content {
  position: absolute;
}

dialog-modal > div {
  display: none;
  height: 100vh;
  width: 100vw;
  position: absolute;
}

dialog-modal > div > button.modal-overlay {
  height: 110vh;
  width: 110vw;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  opacity: 0.6;
  background-color: black;
}

dialog-modal > div > .modal-body {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  padding: 1rem;
  background: white;
}

/* Set main to visibility hidden if modal open */
/* :not([inert]) so when PE inert added visibility is not used */
.main-content:not([inert]):has(input[form="modal-form-my-modal"]:checked) {
  visibility: hidden;
}

/* Set modal to visible if modal open */
body:has(input[form="modal-form-my-modal"]:checked) #modal-container-my-modal {
  display: block;
}

/* ignore basic styles below */
html {
  margin: auto;
  line-height: 1.75;
  font-size: 1.25em;
}

button {
  font-style: san-serif;
  padding: 2px 5px;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  margin: 3em 0 1em;
}

p,
ul,
ol {
  margin-bottom: 2em;
  color: #1d1d1d;
  font-family: sans-serif;
}

// To simulate disabling JS comment out the
// customElements.define at the bottom of page
class DialogModal extends HTMLElement {
  constructor() {
    super();
    this.form = this.querySelector("form");
    this.inertMain = this.inertMain.bind(this);
    this.unInertMain = this.unInertMain.bind(this);
    this.escClose = this.escClose.bind(this);
    this.enterOpen = this.enterOpen.bind(this);
    this.form.addEventListener("reset", this.unInertMain);
    window.addEventListener("keyup", this.escClose);
  }
  connectedCallback() {
    this.mainContentClass = this.getAttribute("main-content-class");
    this.mainContent = document.querySelector("." + this.mainContentClass);
    this.name = this.getAttribute("name");
    this.allTriggers = document.querySelectorAll(
      "input[type=checkbox][form=modal-form-" + this.name + "]"
    );
    this.allTriggers.forEach((trigger) => {
      trigger.addEventListener("change", this.inertMain);
      trigger.addEventListener("keydown", this.enterOpen);
    });
  }
  disconnectedCallback() {
    this.allTriggers.forEach((trigger) => {
      trigger.removeEventListener("change", this.inertMain);
      trigger.removeEventListener("keydown", this.enterOpen);
    });
    this.form.removeEventListener("reset", this.unInertMain);
    window.removeEventListener("keyup", this.escClose);
  }
  inertMain() {
    this.mainContent.setAttribute("inert", "");
  }
  unInertMain() {
    this.mainContent.removeAttribute("inert");
  }
  enterOpen(e) {
    if (e.code === "Enter") {
      e.target.checked = true;
      this.inertMain();
    }
  }
  escClose(e) {
    if (e.code === "Escape") {
      this.form.reset();
    }
  }
}
customElements.define("dialog-modal", DialogModal);

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.