SOURCE

class UserInfo extends HTMLElement {
    constructor() {
        super();

        const template = document.getElementById('template')
        const content = template.content.cloneNode(true)

        this.appendChild(content);

        this.compilerNode()
    }

    compilerNode() {
        Array.prototype.forEach.call(this.childNodes, (node) => {
            if (node.childNodes.length > 0) {
                this.compilerNode(node.childNodes)
            } else {
                console.log(1, node.nodeName)
            }
        })
    }


}

window.customElements.define('user-info', UserInfo);

<template id="template">
    <div class="container">
        <span class="name"></span>
        <input type="" class="input">
    </div>
</template>
<user-info></user-info>