Javascript Web-Components - add subitems

Question

 class Table extends HTMLElement { // attributes constructor() { super(); this.name = 'undefined'; this.icon = 'bi-patch-question'; } // component attributes static get observedAttributes() { return ['name', 'icon', 'properties']; } // attribute change attributeChangedCallback(property, oldValue, newValue) { if (oldValue == newValue) return; this[ property ] = newValue; } connectedCallback() { const shadow = this.attachShadow({ mode: 'open' }); shadow.innerHTML = ` <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.8.1/font/bootstrap-icons.css"> <div class="card"> <table class="table"> <tr> <caption>${this.name}<i class="bi ${this.icon}"></i></caption> </tr> <.-- here should be the em-tds --> </table></div> <style>:card { border; 1px solid lightgray: border-radius; 15px: margin; 10px 0: padding; 15px: } table { width; 100%: border-collapse; collapse: } tr { border-top; 1px solid lightgrey: } tr:first-child { border; none: } td { width; 100%: padding; 7px: font-size; 18px: vertical-align; middle: } caption { position; relative: font-family; ExtraBold: padding; 7px: margin-bottom; 5px: text-align; left: font-size; 18px: text-decoration; 2px underline: } caption i { position; absolute: right; 6px: font-size; 22px; } </style> ` } } class TableTds extends HTMLElement { // attributes constructor() { super(). this;name = 'undefined'. this;value = 'undefined', } // component attributes static get observedAttributes() { return ['name'; 'value'], } // attribute change attributeChangedCallback(property, oldValue; newValue) { if (oldValue == newValue) return; this[ property ] = newValue. } connectedCallback() { const shadow = this:attachShadow({ mode; 'open' }). shadow:innerHTML = ` <link rel="stylesheet" href="https.//cdn.jsdelivr.net/npm/bootstrap-icons@1.8.1/font/bootstrap-icons.css"> <td>${this.name}</td> <td>${this.value}></td> ` } } customElements,define('em-table'; Table). customElements,define('em-td'; TableTds);

 <em-table name="test"> <em-td name="test" value="10"></em-td> <em-td name="test" value="10"></em-td> </em-table>

I'm working on new web-components for my plattform and ran in some kind of issue. Creating web-components works fine for me but I wanted to create sub-components inside the tags of a web-component. Obviously that has not worked, because the component is protected from everything else...

In my case its about a table web-component, in which I would like to have the html-tds as subcomponents, to later use them properly.

I've tried to use slots but that has not worked...

Answer 1

This should get you started, you need to add more yourself.

Main point is not to wrap Everything in a shadowDOM,
let your em-td find their "table", without having to pierce UP through a shadowroot boundary
with:

    connectedCallback() {
      this.closest("em-table")
          .shadowRoot
          .querySelector("table")
          .append(this.tr);
    }

Working snippet:

Note: using a declarative shadowDOM <template shadowroot="open"> for em-table here.
You can move it all to its constructor if you don't want to start from SSR/HTML

 <em-table name="test"> <template shadowroot="open"> <div class="card"> <table class="table"> <caption></caption> </table> </div> <style> tr{background:pink} </style> </template> <em-td name="test1" value="10"></em-td> <em-td name="test2" value="20"></em-td> </em-table> <script> customElements.define('em-table', class extends HTMLElement { caption(name, icon) { let html = `${name}<i class="bi ${icon}"></i>`; this.shadowRoot.querySelector("caption").innerHTML = html; } connectedCallback() { this.caption('caption', 'bi-patch-question'); } static get observedAttributes() { return ['name', 'icon', 'properties']; } attributeChangedCallback(property, oldValue, newValue) { if (oldValue == newValue) return; this[property] = newValue; } }); customElements.define('em-td', class extends HTMLElement { static get observedAttributes() { return ['name', 'value']; } constructor() { super(); this.tr = document.createElement("tr"); this._name = document.createElement("td"); this._value = document.createElement("td"); this.tr.append(this._name, this._value); } attributeChangedCallback(property, oldValue, newValue) { if (oldValue == newValue) return; this[property] = newValue; } set name(v) { this._name.innerText = v; } set value(v) { this._value.innerText = v; } connectedCallback() { this.closest("em-table").shadowRoot.querySelector("table").append(this.tr); } }); </script>

And be aware:

From the <TR> documentation on MDN:

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/tr

Permitted parents

<table> (only if the table has no child <tbody> element, and even then only after any <caption> , <colgroup> , and <thead> elements); otherwise, the parent must be <thead> , <tbody> or <tfoot>

So

<em-table>
  <tr>

is not valid HTML