Google Certified Mobile Web Specialist Study Notes

By Waicung in Web Development — Jan 11, 2019

Basic Website Layout and Styling

Mobile Emulation

Viewport

<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- 
    device-width = DIP
    initial-scale: DIP:CSS Pixel = 1:1
-->

Mobile assume all sites with a width of 980px unless viewport defined
Device Independent Pixels(DIP): relate pixels to real distance
Device Pixel Ratio(DPR) = Hardware Pixels / Device Independent Pixels
Font boosting: scale up auto-detected primary content

Relative Element Width

disable overflow

img, embed, object, video {
    max-width: 100%;
}

Not overflow or Absolutely smaller than any viewport(320px)

Tap/Touch Target Sizes

Minimum size 48px X 48px
Rooms in between 40px:

.list-item a {
    padding: 1.5em inherit
}
.nav-item a {
    padding: 1.5em
}

Design and Prioritising Content

Start Small

Selectively apply CSS

More HTTP requests

<link rel="stylesheet" media="screen and (min-width:500px)" href="over500.css">

Fewer HTTP requests, larger files

@media screen and (min-width: 500px) {
    body {}
}

Expensive method (should be avoid)

@import url("over500.css") only screen and (min-width: 500px);

Based on browser width
min-width: apply when larger than the defined value
max-width: apply when smaller than the defined value

Based on devide width
min-device-width:
max-device-width:

Breakpoints

Content Based Breakpoint Selection: Add a breakpoint when the content start to look weird

Complex Media Queries

Apply when viewpoint is in between 300px and 600px

@media screen and (min-width: 300px) and (max-width: 600px) {
    ...
}

Grids

Bootstrap

Flexbox

display:flex define flex container
flex-wrap:wrap define whether flex container wrap inside items
order:n use with flex item for flex order inside a flex container
width use with order to achieve a full-width layout with multiple element

Responsive Pattern

Column Drop: (Single Column)Stack elements -> Multiple Columns

Mostly Fluid:

More grid-like, More Columns fit in different way
Margin in widest viewport

flex-container {
    width: 700px;
    margin-left: auto;
    margin-right: auto;
}

Layout Shifter:

Most responsive
Require more planning
Use the flex item order attribute

Off Canvas

Place content off screen
Only display if screen large enough
For example, navigation menu

nav {
  width: 300px;
  background-color: #ffffff;
  z-index: 10;
  position: absolute;
  /* This trasform moves the drawer off canvas. */
  -webkit-transform: translate(-300px, 0);
  transform: translate(-300px, 0);
  /* Optionally, we animate the drawer. */
  transition: transform 0.3s ease;
}
nav.open {
  -webkit-transform: translate(0, 0);
  transform: translate(0, 0);
}

Javescript to toggle the menu

var menu = document.querySelector('#menu');
var main = document.querySelector('main');
var drawer = document.querySelector('.nav');

menu.addEventListener('click', function(e) {
    drawer.classList.toggle('open');
    e.stopPropagation();
});
main.addEventListener('click', function() {
    drawer.classList.remove('open');
});

Responsive Table

hide columns
position header off screen
pull data from content
- content: attr(data-th);

td { 
    position: relative;
    padding-left: 50%; 
}

td:before { 
    position: absolute;
    left: 6px;
    content: attr(data-th);
    font-weight: bold;
}

Tontained Scrolling Table

div {
    width: 100%;
    overflow-x: auto;
}

Vertical Tables (When Applicable)

disable table layout with display:block
hide table header thead by push it off screen so that it can still be read
place header in front of each data with custom data attribute
bold to highlight 'headers'

@media screen and (max-width: 500px) {
    table, thead, tbody, th, td, tr {
      display: block;
    }
    thead tr {
      position: absolute;
      top: -9999px;
      left: -9999px;
    }
    td { 
      position: relative;
      padding-left: 50%; 
    }

    td:before { 
      position: absolute;
      left: 6px;
      content: attr(data-th);
      font-weight: bold;
    }
    td:first-of-type {
      font-weight: bold;
    }
}

Fonts

Base font
font-size: 16px
line-height: 1.2em

Ideal Measure of Lines

45-90 cpl
65 for the web

Minor Breakpoints

Long Text Ellipsis

Reponsive Images

max-width:100%;

50% width with 10px space in between

img {
    margin-right: 10px;
    max-width: 426px;
    width: calc((100% - 10px)/2);
}
img:last-of-type {
    margin-right: 0;
}

calc((100% - 20px)/3);

A space is required around + and - operators
with * and /, spaces are not required
the problem is an ambiguity around negation

Landscape and Portrait

responsively cover the whole height of the viewport: 100vh => 100% height
100vw => 100% width
100vmin: 100% shorter side of the viewport
100vmax: 100% longer side of the viewport

Raster and Vector

PNG v SVG

Automation Tools

Grunt: Task Runner
ImageMagick: Image Processing Tool

Text & Images

Font over images
Avoid using images but a decent layout and font
Use Images sparingly

CSS Background Techniques

background:cover
CSS gradient
CSS elaborate
Conditional image display

@media screen and (max-width: 500px)
div.photo {
    background-image: none;
    height: 0;
    margin: 0;
    width: 0;
}
div.photo {
    background-size: cover;
    float: left;
    margin: 0 2vw 1vw 0;
    height: 50vw;
    position: relative;
    top: 3px;
    transition: all 0.5s;
    width: 50vw;
}

Alternative images

@media screen and (max-width: 500px)
div {
    background-image: url(koala_crop.jpg);
}
div {
    background-image: url(koala.jpg);
    background-size: cover;
    height: 50vw;
    transition: background-image 2s;
    width: 50vw;
}

image-set(): ideal for icon display

div {
    background-image: url(icon1x.png);
    background-image: -webkit-image-set(url(icon1x.png) 1x, url(icon2x.png) 2x);
    background-image: image-set(url(icon1x.png) 1x, url(icon2x.png) 2x);
    height: 128px;
    width: 128px;
}

Contain & Cover

background-size:contain => shorter dimension of the background image might be shorter than the container
background-size:cover => longer dimention may be covered by the container

Unicode to replace image

<meta charset="utf-8" >

ICON Fonts

Inline SVG & Data URI

Data URI (to inline images, less HTTP request)
SVG Optimiser
SVG Animation

srcset

assume images display full viewport width
1x & 2x: Pixel Density Descriptor
w: Tells browser about image width dimensions

size Attribute: indicate display size of an image

sizes="50vw"
sizes="(max-width: 250px) 100vw, 50vw"

picture & source element

picture: container for sources
source: alternative image sources
img: fallback but compulsory, the actual element display the images
WebP

<picture>
  <source srcset="kittens.webp" type="image/webp">
  <source srcset="kittens.jpeg" type="image/jpeg">
  <img src="kittens.jpg" alt="">
</picture>

source with media attribute

<picture>
  <source media="(min-width: 1000px)" srcset="kookaburra_large_1x.jpg 1x, kookaburra_large_2x.jpg 2x">
  <source media="(min-width: 500px)" srcset="kookaburra_medium_1x.jpg 1x, kookaburra_medium_2x.jpg 2x">
  <img src="kookaburra_small.jpg" alt="The kookaburra: a terrestrial tree kingfisher native to Australia and New Guinea (according to Wikipedia)">
</picture>

grunt guide

Final Code

Responsive Images Community Group

<figure>
    <picture>
      <source media="(min-width: 750px)" srcset="images/volt-1600_large_2x.jpg 2x, images/volt-800_large_1x.jpg"  />
      <source media="(min-width: 500px)" srcset="images/volt_medium.jpg" />
      <img src="images/volt_small.jpg" alt="Volt sign in old Berlin power station">
    </picture>
    <figcaption>Sign in old Berlin power station</figcaption>
</figure>

Flexbox

Container

display
flex-direction: row | row-reverse | column | column-reverse;
- row ltr
- column top to bottom
flex-wrap
flex-flow: flex-direction flex-wrap
justify-content: flex-start | flex-end | center | space-between | space-around | space-evenly;
align-items: flex-start | flex-end | center | baseline | stretch;
align-content: flex-start | flex-end | center | space-between | space-around | stretch;

Items

order: ;
flex-grow: ;
flex-shrink: ;
flex-basis: | auto;
flex: none | [ <'flex-grow'> <'flex-shrink'>? || <'flex-basis'> ]
align-self: auto | flex-start | flex-end | center | baseline | stretch;

Autoprefixer

npm install grunt-cli grunt-contrib-watch grunt-autoprefixer

grunt

module.exports = function (grunt) {
    grunt.initConfig({
        autoprefixer: {
            dist: {
                files: {
                    'build/style.css': 'style.css'
                }
            }
        },
        watch: {
            styles: {
                files: ['style.css'],
                tasks: ['autoprefixer']
            }
        }
    });
    grunt.loadNpmTasks('grunt-autoprefixer');
    grunt.loadNpmTasks('grunt-contrib-watch');
};

Media Queries

@media speech and (min-width: 30em) and (orientation: landscape) { ... }
@media (min-height: 680px), screen and (orientation: portrait) { ... }

Media types

all
print
screen
speech

Media Features

width&height
aspect-ratio
orientation
resolution
hover
light-level
monochrome

Logical Operations

and combines multiple media features
not [Media Type]
only [Media Type]
, combines multiple media queries ( || )

not: is evaluated last

@media not all and (monochrome) { ... }

is the same as

@media not (all and (monochrome)) { ... }

Media Query Level 4

@media (width <= 30em) { ... }
@media (30em <= width <= 50em ) { ... }
@media (not(hover)) { ... }

Audio and Video

Video

<video controls>
  <source src="rabbit320.mp4" type="video/mp4">
  <source src="rabbit320.webm" type="video/webm">
  <p>Your browser doesn't support HTML5 video. Here is a <a href="rabbit320.mp4">link to the video</a> instead.</p>
</video>

width & height
autoplay
loop: re-play automatically
muted
poster: display before the video is played
preload: none | auto | metadata

Audio

<audio controls>
  <source src="viper.mp3" type="audio/mp3">
  <source src="viper.ogg" type="audio/ogg">
  <p>Your browser doesn't support HTML5 audio. Here is a <a href="viper.mp3">link to the audio</a> instead.</p>
</audio>

Video Text Tracks

Subtitles
Captions
Timed descriptions

WEBVTT

Chapter 1
00:00:01.000 --> 00:00:02.000
Introduction to HTML5

Chapter 2
00:00:03.001 --> 00:00:04.000
Introduction to Chapter 2
  ...

<video controls>
    <source src="example.mp4" type="video/mp4">
    <source src="example.webm" type="video/webm">
    <track kind="subtitles" src="subtitles_en.vtt" srclang="en">
</video>

srt to vtt

Touch Event

// [concurrent "touch AND mouse/keyboard" event binding](https://w3c.github.io/touch-events/#mouse-events)

// set up event listeners for touch
target.addEventListener('touchend', function(e) {
  // prevent compatibility mouse events and click
  e.preventDefault();
  ...
});
...

// set up event listeners for mouse/keyboard
target.addEventListener('click', ...);
...

touchstart
Zero or more touchmove
touchend
touchcancel
mousemove
mousedown
mouseup
click

TouchEvent: an event that occurs when the state of touches on the surface changes

Touch: a single point of contact

TouchList: a group of touches

Front End Networking

fetch() & Promises

fetch('./api/some.json')
  .then(
    function(response) {
      if (response.status !== 200) {
        console.log('Looks like there was a problem. Status Code: ' +
          response.status);
        return;
      }

      // Examine the text in the response
      response.json().then(function(data) {
        console.log(data);
      });
    }
  )
  .catch(function(err) {
    console.log('Fetch Error :-S', err);
  });

Response Types

basic: a resource on the same origin
cors: a resource on another origin which returns the CORs headers
- restricts the headers you can view to
  - Cache-Control,
  - Content-Language,
  - Content-Type,
  - Expires,
  - Last-Modified, and
  - Pragma.
opaque: a request made for a resource on a different origin that doesn't return CORS headers

Defined fetch request mode

same-origin: only same origin request succeeds
cors: allow same origin and also other origins with CORs headers
cors-with-forced-preflight: always perform a preflight check
no-cors: make requests to other origins with no CORS headers in return (Not possible yet July 2, 2018)

fetch('http://some-site.com/cors-enabled/some.json', {mode: 'cors'})
  .then(function(response) {
    return response.text();
  })
  .then(function(text) {
    console.log('Request successful', text);
  })
  .catch(function(error) {
    log('Request failed', error)
  });

Chaining Promises

benefit: share logic across fetch requests

function status(response) {
  if (response.status >= 200 && response.status < 300) {
    return Promise.resolve(response)
  } else {
    return Promise.reject(new Error(response.statusText))
  }
}

function json(response) {
  return response.json()
}

fetch('users.json')
  .then(status)
  .then(json)
  .then(function(data) {
    console.log('Request succeeded with JSON response', data);
  }).catch(function(error) {
    console.log('Request failed', error);
  });

Post Request

fetch(url, {
    method: 'post',
    headers: {
      "Content-type": "application/x-www-form-urlencoded; charset=UTF-8"
    },
    body: 'foo=bar&lorem=ipsum'
  })
  .then(json)
  .then(function (data) {
    console.log('Request succeeded with JSON response', data);
  })
  .catch(function (error) {
    console.log('Request failed', error);
  });

Credential

fetch('https://example.com', {
  credentials: 'include'  
})

'same-origin': only send on the same origin
'omit': not to include credentials

Second Parameter, an init object

fetch(url, {
    method: "POST", // *GET, POST, PUT, DELETE, etc.
    mode: "cors", // no-cors, cors, *same-origin
    cache: "no-cache", // *default, no-cache, reload, force-cache, only-if-cached
    credentials: "same-origin", // include, *same-origin, omit
    headers: {
        "Content-Type": "application/json; charset=utf-8",
        // "Content-Type": "application/x-www-form-urlencoded",
    },
    redirect: "follow", // manual, *follow, error
    referrer: "no-referrer", // no-referrer, *client
    body: JSON.stringify(data), // body data type must match "Content-Type" header
    })
    .then(response => response.json()); // parses response to JSON

Uploading JSON data

var url = 'https://example.com/profile';
var data = {username: 'example'};

fetch(url, {
  method: 'POST', // or 'PUT'
  body: JSON.stringify(data), // data can be `string` or {object}!
  headers:{
    'Content-Type': 'application/json'
  }
}).then(res => res.json())
.then(response => console.log('Success:', JSON.stringify(response)))
.catch(error => console.error('Error:', error));

Uploading a file

var formData = new FormData();
var fileField = document.querySelector("input[type='file']");

formData.append('username', 'abc123');
formData.append('avatar', fileField.files[0]);

fetch('https://example.com/profile/avatar', {
  method: 'PUT',
  body: formData
})
.then(response => response.json())
.catch(error => console.error('Error:', error))
.then(response => console.log('Success:', JSON.stringify(response)));

Multiple Files

var formData = new FormData();
var photos = document.querySelector("input[type='file'][multiple]");

formData.append('title', 'My Vegas Vacation');
formData.append('photos', photos.files);

fetch('https://example.com/posts', {
  method: 'POST',
  body: formData
})
.then(response => response.json())
.then(response => console.log('Success:', JSON.stringify(response)))
.catch(error => console.error('Error:', error));

Request Object

var myHeaders = new Headers();

var myInit = { method: 'GET',
               headers: myHeaders,
               mode: 'cors',
               cache: 'default' };

var myRequest = new Request('flowers.jpg', myInit);

fetch(myRequest).then(function(response) {
  return response.blob();
}).then(function(myBlob) {
  var objectURL = URL.createObjectURL(myBlob);
  myImage.src = objectURL;
});

Headers interface

Content-Type
Content-Length
X-Custom-Header
Set-Cookie
Origin

Check Content Type

fetch(myRequest).then(function(response) {
    var contentType = response.headers.get("content-type");
    if(contentType && contentType.includes("application/json")) {
      return response.json();
    }
    throw new TypeError("Oops, we haven't got JSON!");
  })
  .then(function(json) { /* process your JSON further */ })
  .catch(function(error) { console.log(error); });

Guard

none
request => may not set 'Content-Length'
request-no-cors: for request created with Request.mode=no-cors
response => not allow to insert 'Set-Cookie'
immutable

Response Objects

body

Blob
BufferSource: a typedef
FormData
ReadableStream: a readable stream of byte data
URLSearchParams
USVString: the set of all possible sequences of unicode scalar values

Common Properties

Response.status: An integer(default 200)
Response.statusText: A string(default 'OK')
Response.ok: Boolean (check if status is between 200-299)

Body: an instance of any of the following types

ArrayBuffer: represent a generic, fixed-length raw binary data buffer
ArrayBUfferView: representing any of a group of JavaScript TypedArray
Blob/File: a file-like object of immutable, raw data
string
URLSearchParams: defines utility methods to work with the query string of a URL
FormData: a way to easily construct a set of key/value pairs representing form fields and their values

Extract Methods

arrayBuffer()
blob()
json()
text()
formData()

Feature Detection

if (self.fetch) {
    // run my fetch request here
} else {
    // do something with XMLHttpRequest?
}

polyfill

Stream

Cross-Origin Resource Sharing (CORS)

Accessibility

Web Fundamentals – Accessibility

Web Content Accessibility

Preceivable
Operable
Understadable
Robust

Focus

Built-in interactive HTML elements are implicity focusable
- automatically inserted into the tab order
- have built-in keyboard event handling

Semantics

Assistive technology
Affordances
Screen readers
- The element's role or type, if it is specified (it should be).
- The element's name, if it has one (it should).
- The element's value, if it has one (it may or may not).
- The element's state, e.g., whether it is enabled or disabled (if applicable).

Styling

styles for focus and various ARIA states

Styling focus

/* At a minimum you can add a focus style that matches your hover style */
:hover, :focus {
  background: #c0ffee;
}

-Input modality: show button when input by keyboard

fake-button {
    display: inline-block;
    padding: 10px;
    border: 1px solid black;
    cursor: pointer;
    user-select: none;
  }

  fake-button:focus {
    outline: none;
    background: pink;
  }

Styling states with ARIA
.toggle[aria-pressed="true"] { ... }

can be zoomed or scaled to accommodate users
- Multi-device responsive design
  - <meta name="viewport" content="width=device-width, initial-scale=1.0">
  - A minimum recommended touch target size is around 48 device independent pixels
Choosing the right colors and contrast
- A (minimum) contrast ratio of 4.5:1
- Color Contrast Checker