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Web Component Design Designing Frontends for Reusability TEGERNSEE, 23 FEB 2019
 JOY HERON

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2 Web Component Design Joy Heron Consultant @ INNOQ joy.heron@innoq.com @iamjoyheron

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3 Web Component Design Photo by Brett Patzke on Unsplash My Journey

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4 Spring 2016 Web Component Design

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5 Web Component Design Spring 2016 Summer 2016 Spring 2017 Winter 2017 Fall 2018 … and in the future??

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6 Web Component Design Why am I always implementing the same thing?

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7 Web Component Design Would I do this in the backend? Joy Heron / @iamjoyheron

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8 Web Component Design Abstraction Joy Heron / @iamjoyheron Step 1: copy Step 2: copy Step 3: Abstract!

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9 Time to find an abstraction! Web Component Design GET /search?col1=x&col2=y 200 OK …

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And now let’s build it with web components! 10 Web Component Design That’s what I did. It’s called: Tabelle https://github.com/innoq/tabelle

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11 Web Component Design What is a web component? Joy Heron / @iamjoyheron HTML CSS probably JavaScript possibly make it pretty make it better make it work FOR ALL USERS!

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12 Web Component Design Single Responsibility Principle Joy Heron / @iamjoyheron Each Component should do ONE thing REALLY WELL If you need more functionality, write a new component and compose them! Benefit of HTML First: HTML composes naturally!

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13 Web Component Design How to find web components? Joy Heron / @iamjoyheron Atomic Design: http://atomicdesign.bradfrost.com/

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14 Web Component Design Joy Heron / @iamjoyheron F I R S T C O M P O N E N T

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15 make it work Web Component Design

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16 Web Component Design Filter Field Component Joy Heron / @iamjoyheron Step 1: make it work GET /search? col1=my+search+str& col2=Option+1 What we need Option 1 Option 2 Option 3 Search How to get it

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17 it works! Web Component Design FOR ALL USERS??

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18 Web Component Design Tip #1 If you want to make sure you are accessible ACTUALLY USE A SCREEN READER Joy Heron / @iamjoyheron

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Common Excuses for not using screen readers 19 MORE Web Component Design Joy Heron / @iamjoyheron Apple VoiceOver ChromeVox Orca Excuse #1: I don’t have one! Free Screen Readers:

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Common Excuses for not using screen readers 20 Web Component Design Joy Heron / @iamjoyheron Excuse #2: It’s HARD! Yes. But if you have time to focus on accessibility, then look into it!

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21 Web Component Design DON’T design your components based on how YOU use a screen reader BUT the basic commands are pretty easy to figure out! Read up on Accessibility!!!

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22 Web Component Design let’s try it out… Joy Heron / @iamjoyheron

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23 Web Component Design Joy Heron / @iamjoyheron Currently Edit Text.
 You are currently on a text field inside of web content… Solution Filter Field Component Step 1.2: make it accessible Filter Column 1, Edit Text.
 You are currently on a text field inside of web content… ❤ Let’s test our component with a screen reader to see how it sounds!

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24 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS!

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25 make it pretty?? Web Component Design

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26 CSS is harder to OVERRIDE than it is to WRITE Web Component Design Joy Heron / @iamjoyheron

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27 Web Component Design Tip #2 Use minimal CSS to make it easy to override your styles later! Joy Heron / @iamjoyheron

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28 Web Component Design Joy Heron / @iamjoyheron … Add a CSS class to our component to allow users to write their own styles later! Filter Field Component Step 2: make it pretty

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29 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS! CSS someone else can make it pretty! JS? make it better? ?

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30 Web Component Design Joy Heron / @iamjoyheron CSS someone else can make it pretty! JS no need! HTML it works FOR ALL USERS!

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31 Web Component Design Joy Heron / @iamjoyheron S E C O N D C O M P O N E N T

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32 make it work Web Component Design

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33 Web Component Design Sort Button Component Joy Heron / @iamjoyheron Step 1: make it work GET /search?sort=col1_asc What we need Sort Column 1 Ascending Search How to get it HTML Element? Sort Column 2 Descending

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34 Web Component Design Joy Heron / @iamjoyheron Sort Column 1 Ascending, radio button, 1 of 2
 You are currently on a radio button, 1 of 2, … ❤ Sort Button Component Step 1.2: make it accessible

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35 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS!

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36 make it pretty Web Component Design

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37 Web Component Design Tip #3 You can select an input element by clicking on it’s HTML label Joy Heron / @iamjoyheron

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38 Web Component Design Joy Heron / @iamjoyheron Visually hide radio buttons and style their labels. Sort Button Component Step 2: make it pretty %visually-hidden { position: absolute !important; height: 1px; width: 1px; overflow: hidden; clip: rect(1px 1px 1px 1px); /* IE6, IE7 */ clip: rect(1px, 1px, 1px, 1px); } .visually-hidden { @extend %visually-hidden; } Source: https://snook.ca/archives/html_and_css/hiding-content-for-accessibility Move content offscreen so it is not visible but can still be read by a screen reader. SCSS Placeholder Selector & Util CSS Class

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39 Web Component Design Joy Heron / @iamjoyheron Sort Column 1 Ascending Sort Column 2 Descending Visually hide radio buttons and style their labels. .arrow { @extend %visually-hidden; } .arrow—asc { @include icon-before(‘up.svg’, #acacac); cursor: pointer; } .arrow—desc { @include icon-before(‘down.svg’, #acacac); cursor: pointer; } So far, so good: Sort Button Component Step 2: make it pretty

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40 Web Component Design Joy Heron / @iamjoyheron • Style checked, focused, and hover input states! • Because our label follows our input, we can style this using pure CSS with a ‘+’! .arrow:checked + .arrow—asc::before, .arrow:checked + .arrow—desc::before { background-color: #535353; } .arrow:focus + .arrow—asc::before, .arrow:focus + .arrow—desc::before, .arrow:hover + .arrow—asc::before, .arrow:hover + .arrow—desc::before { background-color: #6882cb; } Result: focused: checked: Sort Button Component Step 2: make it pretty

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41 Web Component Design Joy Heron / @iamjoyheron Hide our labels visually Sort Column 1 Ascending Sort Column 1 Descending base: checked: focused: Sort Button Component Step 2: make it pretty

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42 Web Component Design Joy Heron / @iamjoyheron Sort Button Component Step 2.2: Double-check accessibility Sort Column 1 Ascending, radio button, 1 of 2
 You are currently on a radio button, 1 of 2, … ❤

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43 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS! CSS it’s pretty! JS? make it better? ?

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44 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS! CSS it’s pretty! JS we’re ok for now!

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45 Web Component Design before we move on to the next component… Joy Heron / @iamjoyheron

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46 Web Component Design Tip #4 Use a templating engine as an abstraction for your component Joy Heron / @iamjoyheron

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47 Web Component Design Benefits of HTML Templates for web components Joy Heron / @iamjoyheron Change ONCE, modify all instances Easier to MAINTAIN components over time PUBLISH templates as an npm library for use in other projects

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input and select components 48 Web Component Design Joy Heron / @iamjoyheron {{!— input.hbs }} {{!— select.hbs }} {{> @partial-block}} {{> input name=“col1” label=“Column 1” }} {{#> select name=“col2” label=“Column 2” }} A B … Z {{/select}}

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arrows component 49 Web Component Design Joy Heron / @iamjoyheron {{!— arrows.hbs }} Sort {{label}} Ascending Sort {{label}} Descending {{> arrows name=“col3” label=“Column 3” }}

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50 Web Component Design Joy Heron / @iamjoyheron T H I R D C O M P O N E N T

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51 make it work Web Component Design

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52 Web Component Design Table Header Component Joy Heron / @iamjoyheron Step 1: make it work
Column 1 {{> arrows name=“col1” label=“Column 1” }} {{> input name=“col1” label=“Column 1” }}

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53 Web Component Design Table Header Component Joy Heron / @iamjoyheron Step 1.2: make it accessible Column 1 → Sort Column 1 Ascending, radio button 1 of 6 Sort Column 1 Ascending → → Sort Column 1 Descending, radio button 2 of 6 Sort Column 1 Descending → Filter Column 1, edit text → → Column 2 → Sort Column 2 Ascending, radio button 3 of 6 Sort Column 2 Ascending → → Sort Column 2 Descending, radio button 4 of 6 → …

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54 Web Component Design Tip #5 Wrap input fields in a role=group to add a navigation level for a screen reader Joy Heron / @iamjoyheron Note: The builtin HTML Element fieldset provides similar behavior but is extremely difficult to style

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55 Web Component Design Table Header Component Joy Heron / @iamjoyheron Step 1.2: make it accessible
Column 1 {{> arrows name=“col1” label=“Column 1” }} {{> input name=“col1” label=“Column 1” }}
Column 1 {{> arrows name=“col1” label=“Column 1” }} {{> input name=“col1” label=“Column 1” }}

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56 Web Component Design Table Header Component Joy Heron / @iamjoyheron Step 1.2: make it accessible Column 1, group VO+→ Column 2, group VO + ↓ Column 2 → Sort Column 2 Ascending, radio button 3 of 6 Sort Column 2 Ascending → → Sort Column 2 Descending, radio button 4 of 6 Sort Column 2 Descending → Filter Column 2, edit text → Navigation via groups with a screen reader! ❤

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57 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS!

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58 make it pretty Web Component Design

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R.I.P Whack-A-Mole CSS 59 Web Component Design Joy Heron / @iamjoyheron

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60 Web Component Design Tip #6 Design CSS like a box of chocolates Design your container with love and place your components inside it. (use Flexbox or CSS Grid) Joy Heron / @iamjoyheron

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61 Web Component Design Table Header Component Joy Heron / @iamjoyheron Step 2: make it pretty Define a CSS Grid for Layout HEADER ▲ ▼ SEARCH .tabelle-header { display: grid; grid-template-areas: “header arrow-asc” “header arrow-desc” “search search”; } 1fr Takes up a proportional amount of grid auto grid-template-columns: 1fr auto;

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62 Web Component Design Table Header Component Joy Heron / @iamjoyheron Step 2: make it pretty Place children items in grid HEADER ▲ ▼ SEARCH .tabelle-header { .header { grid-area: header; } .arrow—asc { grid-area: arrow-asc; } .arrow—desc { grid-area: arrow-desc; } .tabelle-input { grid-area: search; } } .tabelle-header { grid-template-areas: “header arrow-asc” “header arrow-desc” “search search”; }

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63 Web Component Design Table Header Component Joy Heron / @iamjoyheron Step 2: make it pretty Add new styling classes Column 1 … Almost there!!!

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64 Web Component Design Tip #7 With CSS Grid or Flexbox, vertical alignment is finally easy! Joy Heron / @iamjoyheron

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65 Web Component Design Table Header Component Joy Heron / @iamjoyheron Step 2: make it pretty Center table header vertically .tabelle-header { .header { align-self: center; } } ❤

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66 Web Component Design Table Header Component Joy Heron / @iamjoyheron Our HTML Template for reuse ❤ {{!— tabelle-header.hbs }}
{{label}} {{> arrows }} {{#if select}} {{> select }} {{else}} {{> input }} {{/if}}

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67 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS! CSS it’s pretty! JS? make it better? ?

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68 Web Component Design Joy Heron / @iamjoyheron Joy Heron / @iamjoyheron HTML it works FOR ALL USERS! CSS it’s pretty! JS no need!

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69 Web Component Design Joy Heron / @iamjoyheron L A S T C O M P O N E N T

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70 Web Component Design make it work

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71 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 1: make it work {{> tabelle-header name=“col1” label=“Column 1” }} {{> tabelle-header name=“col2” label=“Column 2” }} {{> tabelle-header name=“col3” label=“Column 3” }} … Perform Search Wrap in a form so that we can submit user filter queries

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72 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 1: make it work ❤ The magic of FORMS

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73 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS! CSS? make it pretty? ?

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74 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS! CSS someone else can make it pretty!

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75 make it better Web Component Design

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76 Web Component Design Tip #8 Submit forms asynchronously and replace your DOM with the result from the server Joy Heron / @iamjoyheron

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77 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 3: make it better Submitting forms asynchronously // stringify form data as `application/x-www-form-urlencoded` function serializeForm (form) { … } function submit (form) { const uri = serializeForm(form) return fetch(uri) .then(response => response.text()) } ⚠ Only the application happy path is being considered here. Source: https://github.com/FND/uitil

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78 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 3: make it better Replacing the tbody with response HTML function template2dom (htmlString, selector) { let tmp = document.createElement(‘template’) tmp.innerHTML = htmlString.trim() return tmp.content.querySelector(selector) } function replaceTbody (tbody, htmlResponse) { let newTbody = template2dom(htmlResponse, ‘tbody’) tbody.innerHTML = newTBody.innerHTML } ⚠ Only the application happy path is being considered here.

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79 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 3: make it better Override default submit behavior function doSubmit (component, form) { let tbody = component.querySelector(‘tbody’) submit(form) .then(html => replaceTBody(tbody, html)) } function initializeSubmit (component, form) { form.addEventListener(‘submit’, ev => { doSubmit(component, form) ev.preventDefault() }) } ⚠ Only the application happy path is being considered here. Who calls the initialize function?

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80 Web Component Design Historically: adding a component dynamically used to require BOTH the HTML Markup and a function to initialize it Joy Heron / @iamjoyheron

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81 Web Component Design Tip #9 Use Custom Elements to define a custom HTML Element AND define how to initialize it. The browser will then initialize your component for you! Joy Heron / @iamjoyheron

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82 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 3: make it better Custom Elements allow you to define how the component needs to be initialized. class Tabelle extends HTMLElement { connectedCallback () { let form = this.form initializeSubmit(this, form) } get form () { return this.querySelector(‘form’) } } customElements.define('ta-belle', Tabelle) … As soon as ta-belle appears in the DOM, connectedCallback will be called! ✨

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83 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 3: make it better Custom Elements provide scope: this is bound to the HTML Element itself and it’s native JavaScript API class Tabelle extends HTMLElement { connectedCallback () { let form = this.form initializeSubmit(this, form) } get form () { return this.querySelector(‘form’) } } customElements.define('ta-belle', Tabelle)

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84 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 3: make it better Make the implementation more dynamic by triggering submits when an input element changes import { debounce } from ‘util’ class Tabelle extends HTMLElement { connectedCallback () { … form.addEventListener(‘change’, () => doSubmit(this, form)) form.addEventListener(‘keyup’, debounce(300, ev => doSubmit(this, form))) } } Make sure to debounce ‘keyups’ for input[type=text] elements! https://davidwalsh.name/javascript-debounce-function ⚠ Only the application happy path is being considered here.

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85 Web Component Design Tabelle Joy Heron / @iamjoyheron Step 3: Further possible improvements Replace whole instead of for added flexibility Integrate with the History API so the user can go back and forth in their search history Instantiate the filter fields on the client

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86 Web Component Design Joy Heron / @iamjoyheron

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87 Web Component Design Joy Heron / @iamjoyheron HTML it works FOR ALL USERS! CSS it’s pretty! JS faster & dynamic

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88 Web Component Design Joy Heron / @iamjoyheron https://github.com/innoq/tabelle https://github.com/innoq/tabelle_rails_example Thank you! https://tabelle-rails-example.herokuapp.com/