Acknowledgements

The beginning of your journey with Web Components.

Foreword

A brief introduction to the set of specifications called Web Components. We'll introduce you to concepts such as Shadow DOM, HTML templates, Custom Elements v1 and uncover typical use cases for developing Web Components.

Introduction to Web Components

We'll introduce you to the mockups in Figma, the development environment used throughout the book, and other conventions used in this book.

Conventions Used In The Book

A guide for installing various technologies needed prior to coding the exercises in this book.

Setting Up The Development Environment

We'll look at what you'll learn throughout Fullstack Web Components.

Module 1 Summary

Introduction

In Part 1, you'll code a form using several Web Components specifications.

Specification

Part One

By developing the CardComponent, you'll get hands on experience with autonomous custom elements.

Autonomous custom elements

Before you can develop the CardComponent, you'll need to scaffold the component in Storybook.

Template Slots

Shadow DOM provides encapsulation for styling and template. You'll style CardComponent with CSS in the context of the autonomous custom element's Shadow DOM.

Styling CardComponent

Write integration and snapshot tests for CardComponent using Cypress and Storybook Storyshots.

Testing the card

You built an autonomous custom element with Shadow DOM, HTML templates, and ES Modules. Let's reflect on that.

Chapter One Summary

Getting to Know Web Components

Form-associated custom elements allow custom elements to participate in HTML forms. From validation to submission, you'll code a text input end-to-end.

Form-associated custom elements

Scaffold a form-associated custom element named TextInputComponent in Storybook.

TextInputComponent

You'll learn what distinguises a form-associated custom element from an autonomous custom element, the formAssociated property and ElementInternals interface.

Form Associated and ElementInternals

Form-associated custom elements don't come with a pattern that validates an entire form, so you'll implement a pattern that allows form validation.

Handling Validation

Using observedAttributes and attributeChangedCallback to listen and react to changes in custom element attributes.

Listening for attribute changes

You'll style the various interaction states of the TextInputComponent form-associated custom element.

User feedback

We've created a problem by encapsulating the HTMLInputElement by Shadow DOM. The HTMLInputElement API cann't be accessed by the outside world. In this section, you'll fix that by implementing getters and setters that emulate the HTMLInputElement on TextInputComponent.

Emulating HTMLInputElement

You'll update the Story and provide the missing APIs to TextInputComponent that allow the component to fully interact with a HTML form.

Making a form

Reviewing the work completed on the form-associated custom element TextInputComponent.

Chapter Two Summary

You'll code ButtonComponent, a customized built-in element that inherits accessibility characteristics from HTMLButtonElement.

Customized built-in elements

Scaffold the customized built-in element ButtonComponent with Storybook.

Scaffolding ButtonComponent

Customized built-ins can't benefit from the encapsulation provided by Shadow DOM, so you'll have to find another way to style ButtonComponent.

Styling ButtonComponent

Revist the HTML form by making the user experience more accessible.

Making the form accessible

How customized built-in elements can make custom elements more accessible.

Chapter Three Summary

You'll learn best practices for developing a UI Library with Web Components by coding a micro-library, developing two custom elements with the micro-library, and figuring out how to package the UI library for distribution.

UI Library

Part Two

You'll abstract common patterns intro reusable code in a micro-library powered by TypeScript Decorators.

Micro-library

How to code an interface for Web Components with TypeScript decorators that enables declaration of the selector, styles, and template.

Class Decorator

You'll code a method decorator named Listen that binds event listeners to class methods.

Method Decorator

In this chapter you learned how to code a micro-library with TypeScript decorators that streamlines Web Component development.

Chapter Four Summary

You'll investigate multiple methods for components to communicate by coding an editable table.

Component Communication

How to use mock data in Storybook to code Web Components.

Mocking Table Data in Storybook

You'll learn about three methods for custom elements to communicate, attribute drilling, CustomEvent, and BroadcastChannel.

Coding Compound Components

You'll learn about how to create a separation of concerns between the many custom elements that comprise the editable table.

Making the Table Editable

You learned about how to create a separation of concerns between various custom elements in the same user experience flow.

Summary

Compound Custom Elements

You'll learn how to code a common UX pattern (dialogs) using HTML templates and custom elements.

HTML Templates

You'll mock the DialogComponent in Storybook.

Mocking the Dialog in Storybook

You'll make a configurable dialog with custom elements.

DialogComponent

You'll scaffold two custom elements that leverage DialogComponent to display modals and tooltips.

Modal and Tooltip

You'll fix an issue faced in the last section by learning how to query for elements across Shadow boundaries.

Querying DOM Across Shadow Boundaries

You'll control the ordering and event cycle of dialogs with a custom class named DialogStack.

DialogStack

Summarizing the work completed in DialogComponent, ModalComponent, TooltipComponent, and DialogStack.

Chapter Six Summary

Powering Dialogs with HTML Templates

You'll learn best practices for organizing and distributing Web Component UI libraries.

UI Libraries

You'll learn brest practices for distributing Web Components by formatting the code with named exports, configuring the build with Rollup, providing a standard package format, and writing a custom Node.js script that enables you to publish packages.

Distribution

Custom Elements Manifest provides a wealth of information about each component. After generating a manifest, it will provide documentation for each component in Storybook.

Documentation

You'll learn how to setup continuous integration for the UI library with Github Actions.

Continuous Integration

Let's reflect on the best practices you learned for distributing UI libraries filled with Web Components.

Chapter Seven Summary

Distributing Custom Element Libraries

You'll integrate the UI library with a single-page application and code the end-to-end user experience with custom elements.

Application

Part Three

You'll provide a separation of concerns with custom elements in a single page application.

Application Development with Custom Elements

You'll scaffold the landing page with an autonomous custom element named MainView.

Landing Page

You'll code a global header with autonomous custom elements named AppHeader.

Header

You'll code another autonomous custom element that handles cookie authorization named CookieFooter.

CookieFooter

You'll lazyload an image with customized built-ins.

Background

You developed the landing page of the application, learning how to architect a separation of concerns between the UI components.

Chapter Eight Summary

To handle multiple views in the single page application, you'll need to implement a router that can navigate between each view.

Routing Custom Elements in a SPA

You'll code the Router class that handles the creation and removal of views in the application.

Routing

You'll code the necessary components and services required in the login view.

Login View

Integrate TableCardComponent into a third view of the single page application, the dashboard.

Dashboard View

You coded a single page web application with custom elements and a custom router.

Chapter Nine Summary

You'll server-side render the views of the application with Declarative Shadow DOM and @lit-labs/ssr

Server-Side Rendering Custom Elements

You'll declare a server-side renderable Declarative Shadow DOM HTML template for each component.

Declarative Shadow DOM Templates

To get custom elements to work in Node.js, you'll need to polyfill DOM APIs. Luckily, @lit-labs/ssr provides a tool that enables just that.

Shim

You'll develop Express middleware that server-side renders Declarative Shadow DOM HTML Templates with @lit-labs/ssr.

Express Middleware

You rendered custom elements server-side using Declarative Shadow DOM and @lit-labs/ssr.

Chapter Ten Summary

Server-side Rendering with Declarative Shadow DOM

The conclusion of the book Fullstack Custom Elements.

Conclusion

Fullstack Web Components

Enter your name and email address below, then click the **"Send my free chapter"** button to get started

There are several books about Web Components, but none go into how to integrate Web Components in a typical enterprise web development workflow. This book is designed to help you learn Web Components and integrate it into your work.

In this book, we cover the basics of Web Components, how to code complex user interfaces with custom elements in Storybook, how to test and maintain UI libraries built with custom elements, and how to build web applications entirely with Web Components and browser specifications. It comes with complete code examples. We walk through the entire process step-by-step.

It's taught by Stephen Belovarich, a software engineer and web developer. Stephen has provided what he's learned about UI libraries and web applications while working at Ubiquiti Networks, Norton, Nike, NBC Universal, and Workday, that can benefit other developers, students, and anyone making a website.

The Complete Guide to Building UI Libraries with Web Components

In this book, we will learn Web Components through the lens of a JavaScript developer.

The basics of working with and manipulating Web Components

The best practices for maintaining a UI library made of custom elements

How to create a micro-library for Web Components with TypeScript Decorators

What problems Web Components can solve in everyday development

How to build web applications entirely from Web Components and JavaScript

Programmatically making a template used to be difficult. Templating HTML was either the purview of ES2015 template strings or the domain of JavaScript frameworks. Either way, HTML templates were bundled into JavaScript, separated from the DOM where they were native. This is even the case in the UI library that you've been working on in the course of this book. HTML templates are declared in ES2015 template strings and packaged with the component.

const shadowRoot = this.attachShadow({ mode: "open" });
const template = document.createElement("template");
template.innerHTML = `
<div class="control">
  <input type="text" />
</div>
<div class="message"></div>
`;
shadowRoot.appendChild(template.content.cloneNode(true));

When creating a HTML template dynamically with JavaScript, you used 

 like you would when instantiating any DOM node, passing in the 

 to a custom template declared as an ES2015 template string. 

 differ itself from other DOM nodes in at least two important ways. Instances of 

, which is unlike other DOM nodes which lack this property. The 

 allows you to copy the HTML template that was originally set with 

 and use it in the context of other methods like 

. You can essentially reuse HTML templates as if they were a rubber stamp. Each time 

So far, we haven't harnessed the full potential of HTML templates. Instances of 

 declared in DOM (not created dynamically like in the above example) are not parsed by the user agent, they are essentially hidden from users. You could place an HTML template in the document and the elements contained within the template won't be rendered until the template is cloned. Below is the same HTML template as it would appear if in the DOM.

Using DOM to store HTML templates seems natural. When server-side rendered (SSR), HTML templates can be a powerful means to reuse templates. If SSR were implemented with some sort of metadata engine, each SSR rendered page could render initially with the HTML templates required for the user experiences on that page. In the context of single-page applications (SPA), the appeal of HTML templates may not seem obvious. Templates may be bundled with the SPA and parsed as JavaScript, although this bloats the JavaScript bundle. What if HTML templates could be attached to each route via the SPA router and appended to DOM so they could be reused? Perhaps there are templates in a global scope of an application, like in the case of a "discard changes" or "are you sure?" dialog, where the user must confirm they want to proceed. The HTML template could be stored in DOM and reused throughout the application.

Dialogs seem like a good fit for HTML templates. If we coded a dialog custom element, it would be tempting to provide an inline template, but we could code the dialog in such a way that queries for HTML templates that exist in DOM and reuses them. This way, the dialog would only be concerned with positioning, or in the case of multiple instances of the dialog, the layer in which the dialog is drawn. By creating a separation of concerns between template and dialog, we can reduce code duplication in an application. The HTML template could be declared once with an identifier and instances of dialogs could query for the template and clone template content upon instantiation.

 that manages the state of a dialog instance (open or closed), the type of dialog that should be instantiated, and the dialog's relationship with the DOM element that triggers the dialog to open (an instance of 

 most likely). This new component will query for HTML template and pass a clone of the template to the custom element that should be displayed. 

 won't handle any display characteristics of the displayed user interface of a dialog, the instance of the 

 will essentially be hidden from the user experience. In this way, this is the first time we're using a custom element 

 that updates both "model" and "view" in the traditional sense of MVC. 

 doesn't have to be a custom element, although by making it one we can give engineers the ability to declare instances of 

 in a template, which may seem more intuitive.

---
title: HTML Templates
description: You'll learn how to code a common UX pattern (dialogs) using HTML templates and custom elements.
role: "INTRODUCTION"
isPublicLesson: true
---

# Chapter Six

## HTML Templates

Programmatically making a template used to be difficult. Templating HTML was either the purview of ES2015 template strings or the domain of JavaScript frameworks. Either way, HTML templates were bundled into JavaScript, separated from the DOM where they were native. This is even the case in the UI library that you've been working on in the course of this book. HTML templates are declared in ES2015 template strings and packaged with the component.

```typescript
const shadowRoot = this.attachShadow({ mode: "open" });
const template = document.createElement("template");
template.innerHTML = `
<div class="control">
  <input type="text" />
</div>
<div class="message"></div>
`;
shadowRoot.appendChild(template.content.cloneNode(true));
```

When creating a HTML template dynamically with JavaScript, you used `document.createElement` like you would when instantiating any DOM node, passing in the `string` `template` to hold a reference to a `HTMLTemplateElement`. You then set the `innerHTML` of the `HTMLTemplateElement` to a custom template declared as an ES2015 template string. `HTMLTemplateElement` differ itself from other DOM nodes in at least two important ways. Instances of `HTMLTemplateElement` have a property named `content`, which is unlike other DOM nodes which lack this property. The `cloneNode` method on `content` allows you to copy the HTML template that was originally set with `innerHTML` and use it in the context of other methods like `appendChild`. You can essentially reuse HTML templates as if they were a rubber stamp. Each time `cloneNode` is called in the context of `appendChild` you are stamping the HTML template.

So far, we haven't harnessed the full potential of HTML templates. Instances of `HTMLTemplateElement` declared in DOM (not created dynamically like in the above example) are not parsed by the user agent, they are essentially hidden from users. You could place an HTML template in the document and the elements contained within the template won't be rendered until the template is cloned. Below is the same HTML template as it would appear if in the DOM.

```html
<template>
  <div class="control">
    <input type="text" />
  </div>
  <div class="message"></div>
</template>
```

Using DOM to store HTML templates seems natural. When server-side rendered (SSR), HTML templates can be a powerful means to reuse templates. If SSR were implemented with some sort of metadata engine, each SSR rendered page could render initially with the HTML templates required for the user experiences on that page. In the context of single-page applications (SPA), the appeal of HTML templates may not seem obvious. Templates may be bundled with the SPA and parsed as JavaScript, although this bloats the JavaScript bundle. What if HTML templates could be attached to each route via the SPA router and appended to DOM so they could be reused? Perhaps there are templates in a global scope of an application, like in the case of a "discard changes" or "are you sure?" dialog, where the user must confirm they want to proceed. The HTML template could be stored in DOM and reused throughout the application.