Custom Element Extends in LWC

Question

I am trying to expand HTML Element and I have a problem. Can't Custom Elements be defined in LWC?

Script

export default class DropBox extends LightningElement {
    connectedCallback(){
        // Input Element Extend
        class DropBoxInput extends HTMLInputElement {
            constructor() {
                super();
                this.addStyle();
            }
            addStyle(){
                // Some Style...
            }
        }
        customElements.define('dropBox-input',DropBoxInput,{extends:'input'});
   }
}

Template

<template>
    <input type="text" is="dropBox-input"/>
</template>

When I tried to save the code, I got a message that the "is" property was not available.

Is there a way to define Custom Element at LWC?

Answer 1

according to documents, The secure window does not support 'Custom Element'

Thus, it seems impossible for developers to define Custom Element or expand the Standard Element within the Lightning Web component.