Advanced JavaScript

Transcript

1. Advanced JavaScript Creating Modern Web Applications @BastianHofmann
2. Fancy title, isn't it? but what is it about
3. it's about JS, how you can build rich web applications with it, and how you can enhance your app with fancy features. by the way, when i saw the logo first
4. Let's go back in time to illustrate that .. about 15 years ago
5. the web looked like this
6. or more seriously like, this. lot's of pages linked together, some forms, but far way from the user experience a desktop app had
7. here ebay from back then. overall what you could do with a web app was very limited, images, text, forms, animated gifs, background music, marquee text, js was considered security risk, turn it off, due to features not available in browser, low bandwith
8. php 3 was out, who was around back then doing php? and hey y2k compliant
9. Fast forward to today
10. web sites, no web apps look more like this, rich application, desktop like feeling, offline capabilities, responsive
11. other example: maps
12. or whole ides in the browser
13. So what will we cover today? what will this talk be about?
14. •Web Application development •WebSockets •OEmbed and Caja •APIs and OAuth2 •Real-Time updates PubsubHubbub •WebRTC we'll talk about several techniques to create such rich, responsive web applications, some so brand new that they are only available in dev channel or nightly builds and some that you can use now in your existing apps
15. A few words about me before that ...
16. i work at researchgate, the social network for scientists and researchers
17. ResearchGate gives science back to the people who make it happen. We help researchers build reputation and accelerate scientific progress. On their terms. ‟ the goal is to give...
18. over 2.5 million users
19. here some impressions of the page
20. we are hiring, talk to me if you want
21. have this, and also work on some cool stuff
22. in addition to this i also speak frequently on conferences throughout the world
23. work and live in berlin
24. http://speakerdeck.com/u/bastianhofmann the slides with speaking notes will be available on speakerdeck after the talk
25. ? how about you? languages you use regularly? have your own product? agency work? long lived, short lived projects? large codebases? frameworks you use? js experience?
26. Let's start
27. http://www.meteor.com the app is going to be based on meteor js, a js framework that combines server side and client side programming which reduces the amount of boilerplate code you have to write for server to client communication tremendously, still very early, in some areas limited, but really fun to develop with
28. https://github.com/bashofmann/adv_js_demo/ the code is available on github, so you can check it out later and revisit what i did, run it, debug it, play around with it
29. Let‘s start
30. demo: basic setup, authorization, displaying the feed, input form, instant updated, websocket communication
31. Fancy, but what's in it for me? now you may ask ...
32. Legacy Project because you most likely have a ...
33. Lot's of things! actually there are lot's of things you can use today in your old, existing project (if time war story refactoring the researchgate codebase)
34. CSS Bastian first of all this is my relationship with css
35. http://twitter.github.com/bootstrap so to make it easier for you, you can look at a very good css framework and see how they are doing stuff, e.g. at researchgate we are not using bootstrap, but modeled some of our css after it
36. Good starting point when refactoring your CSS it's a ...
37. Templates next ...
38. var html="<ul>"; for (var i=0; i < viewers.length; i++) { html += "<li>" + viewers[i].displayName + "</li>"; } html += "<ul>"; document.getElementById("#div").innerHTML = html; Where is the error? oftentimes you see something like this in js applications, you iterate over some data, concatenate an html string, and put that into some dom node where is the error? problems: 1st xss, 2nd structure not visible, no code highlights, no ide support, easy to make errors 3rd if your app get's bit, hard to find where the markup is coming from, 4th we are forgetting everything we learned with server side development of web apps, mvc, separation of concerns
39. Templates so, use ....
40. Mustache.JS https://github.com/janl/mustache.js } there are lot's of js templating languages, some examples
41. Hogan.js } http://twitter.github.com/hogan.js/ mustache but with precompiled templates -> faster
42. http://handlebarsjs.com/ also a mustache dialect, compatible but with more features, we are using that one in meteor
43. Two-way communication the last thing you saw in the demo was ... ... which means the app updates when something happens automatically, no reloads necessary
44. WebSockets http://dev.w3.org/html5/websockets/ one way to do this is websockets, if this is not available, you can fall back to other techniques, long polls, short polls, flash, ...
45. socket.io http://socket.io/ libraries helping you with that, e.g. ...
46. SockJS http://sockjs.org/ .. this one is used by meteor
47. http://jwebsocket.org/ implementation on the backend: java
48. http://www.html5rocks.com/en/ tutorials/websockets/basics/ if you want to know how websockets work, read the spec, and/or this blog article
49. Now that we did the groundwork, let's have some fun!
50. MashUps lets mash or app up with some external data
51. cool video: http:// www.youtube.com/ watch?v=OFzkTxiwziQ as you saw in the stream you often times have status updates like this one, with a link, wouldn't it be nice to not only have the link but also a preview of what's behind the link under it. of course youtube offers embedding videos in other pages through an iframe, so you could parse the url, see that it's youtube, parse out the video id, put it into the iframe url, but what if youtube changes the embed tag? what if you want to support more than youtube? lots of work to build and maintain...
52. OEmbed http://oembed.com/ fortunately there is a protocol helping us with that
53. http://www.youtube.com/watch? v=OyJd2qsRkNk in oembed if you have url like
54. you make a get request to it and get back the html page, in the head there are some links pointing to an oembed endpoint ('application/json|xml+oembed)
55. http://www.youtube.com/oembed?url=http%3A %2F%2Fwww.youtube.com%2Fwatch%3Fv %3DOyJd2qsRkNk&maxwidth=500&format=json if you query this endpoint
56. { "provider_url":"http:\/\/www.youtube.com\/", "title":"Jupiter Jones - Das Jahr in dem ich schlief (Musik Video)", "html":"\u003cobject width=\"500\" height=\"306\"\u003e \u003cparam name=\"movie\" value=\"http:\/\/www.youtube.com\/v\/ OyJd2qsRkNk?version=3\"\u003e\u003c\/param\u003e\u003cparam name= \"allowFullScreen\" value=\"true\"\u003e\u003c\/param\u003e \u003cparam name=\"allowscriptaccess\" value=\"always\"\u003e \u003c\/param\u003e\u003cembed src=\"http:\/\/www.youtube.com\/v\/ OyJd2qsRkNk?version=3\" type=\"application\/x-shockwave-flash \" width=\"500\" height=\"306\" allowscriptaccess=\"always \" allowfullscreen=\"true\"\u003e\u003c\/embed\u003e\u003c\/object \u003e", "author_name":"St182", "height":306, "thumbnail_width":480, "width":500, "version":"1.0", "author_url":"http:\/\/www.youtube.com\/user\/Stinkfist182", "provider_name":"YouTube", "thumbnail_url":"http:\/\/i4.ytimg.com\/vi\/OyJd2qsRkNk\/ hqdefault.jpg", "type":"video", "thumbnail_height":360 } you get back a json object with meta information about the url, title, thumbnail and for videos some html which is the embed tag from youtube in this example
57. cool video: the result may then look like this
58. http://embed.ly/ if we don't want to do all this oembed endpoint lookup and have something more comfortable there is also a web service called embedly, you can just post the url to it and get back the oembed json object
59. OpenGraph http://ogp.me/ other ways to get meta information about a url are
60. <html prefix="og: http://ogp.me/ns#"> <head> <title>The Rock (1996)</title> <meta property="og:title" content="The Rock"/> <meta property="og:type" content="video.movie" /> <meta property="og:url" content="http:// www.imdb.com/title/tt0117500/" /> <meta property="og:image" content="http:// ia.media-imdb.com/images/rock.jpg" /> ... </head> ... </html> with opengraph there are og meta tags in the pages head
61. Twitter Cards
62. <meta name="twitter:card" content="summary"> <meta name="twitter:site" content="@nytimes"> <meta name="twitter:url" content="http:// www.nytimes.com/2012/02/19/arts/music/amid- police-presence-fans-congregate-for-whitney- houstons-funeral-in-newark.html"> <meta name="twitter:title" content="Parade of Fans for Houston’s Funeral"> <meta name="twitter:description" content="..."> <meta name="twitter:image" content="http:// graphics8.nytimes.com/images/2012/02/19/us/ 19whitney-span/19whitney-span- articleLarge.jpg"> also special twitter meta tags in the page's head
63. Microdata http://www.w3.org/html/wg/drafts/ microdata/master/ http://schema.org/ ... and ..
64. Microformats http://microformats.org/ with both these specs you annotate some dom nodes with special classes, used for example in the google search
65. Meta Tags or you can just parse some common meta tags like title or description as a fallback
66. Demo OEmbed
67. So embedding external content
68. Is this safe?
69. External HTML could lead to xss if there are script tags in the html
70. http://embed.ly/ if you use embed.ly you're somehow fine, because they are making sure nothing harmful is in there
71. Trust nobody! but ... (probably not even yourself)
72. Caja http://code.google.com/p/google-caja/ sanitize external html, caja strips out all harmful stuff, like script tags, javascript: urls
73. demo: xss, caja
74. API Access next ...
75. to demo that i'm using status.net, an opensource microblogging platform, just because on conferences i can't rely on wifi. one problem though, we want to make ajax request from js to an external domain
76. Same origin policiy problem: same origin policy, which says you are only allowed to access windows or make ajax request to resources that have the same host name as the page that you are on. very important browser security feature, otherwise you could steal the sessions of all other applications that are currently open or have a running session or permanent login cookie. but for api requests this would be fine, we can trust the api provider not to leak sessions
77. JSONP on way jsonp, a bit hacky, google it if you want details
78. Cross-Origin Resource Sharing much nicer, and good browser support
79. Backend api.twitter.com Client client.net AJAX Access-Control-Allow-Origin: * http://www.w3.org/TR/cors/ with cors, before the browser actually does the ajax request it performs an options request and the api needs to return the access-control-allow-origin header, whose value should match the requesting host. if this is the case the ajax request will be executed
80. Authorization of course most api's need authorization to access user specific resources like the user's home timeline
81. http://oauth.net/ one way to do this in javascript applications is oauth2
82. http://tools.ietf.org/html/rfc6749 it's final :)
83. User-Agent Profile i'll not explain the whole of oauth2, but just what is necessary for js application
84. http://twitter.com/authorize? &clientId=... Open Popup lanyrd.com it works like this, on the client app, lanyrd.com, you click a button, the client opens a new browser window pointing to the authorization endpoint of the api, with the clientId (you need to be preregistered at the api) of the client app (and some other parameters)
85. http://twitter.com/authorize? &clientId=... Open Popup HTTPS GET twitter.com/ authorize lanyrd.com in this popups the api provider asks the user to log in,
86. http://twitter.com/authorize? &clientId=... Open Popup Login twitter.com/ authorize lanyrd.com if he is not
87. http://twitter.com/authorize? &clientId=... Open Popup Grant Permission twitter.com/ authorize lanyrd.com and then to grant the client permission to access the api on the user's behalf
88. HTTPS Redirect RedirectURI#ac cessToken RedirectURI# accessToken lanyrd.com twitter.com/ authorize lanyrd.com if the user said yes, the user gets redirected, still in the popup, to a preregistered redirect callback url, the access token for the api is in the fragment part of this url, this means it will not be sent to the backend and not to any proxies but stays in the browser
89. RedirectURI# accessToken Parse Access Token from Fragment Send it to opening window Close popup lanyrd.com lanyrd.com the callback page can only return some static html and js. the js reads out the fragment, and since callback page and client app in the parent window are on the same hostname, it can call a function at the parent window to pass the access token to the client app and then close itself
90. HTTPS Ajax Request to API Access Token twitter.com lanyrd.com now the client app has the access token and can access the api
91. Storing the access token of course you have to store the access token somewhere. cookie would be one example, but that would send the access token over the wire and we may not want this
92. Local Storage http://www.w3.org/TR/webstorage/ better local storage
93. Get new entries pushed by the API now that we have access to api it would be nice to get new entries of the user who connected to it pushed automatically so that we can include it into our stream
94. PubSubHubbub http://code.google.com/p/pubsubhubbub/ many apis have their own implementations, status.net uses pubsubhubbub, but the principles are often the same
95. retrieves Atom feed with Hub URL Hub posts sth pings every subscriber subscribes for feed acks subscription with pubsubhubbub you subscribe your application (backend) for the users feed at a central hub that is able to provide this users feed. after some subscription pingpong, each time when the user adds a new entry to his feed, it is send to the hub and the hub will forward it to every subscriber (of course only possible backend to backend since the hub can't send it directly to a browser)
96. demo: oauth2, pubsubhubbub, sara, chat
97. http://www.webrtc.org/ next p2p realtime communication between clients, this is possible with webrtc, very new, currently only possible in chrome dev channel and canary and firefox nightly builds, you can exchange any binary data, not only text, audio, video
98. PEERJS http://peerjs.com/ one easy abstraction layer for webrtc just was published a few days ago, called peerjs, only works reliably for text at the moment, due to browser bugs (if even that)
99. http://www.html5rocks.com/en/ tutorials/webrtc/basics/ you can read up details in the spec or here
100. Try it out yourself if you want to ...
101. http://vagrantup.com/ i built a vagrant vm for it
102. $ vagrant up $ vagrant ssh $ cd app $ mrt Follow the readme! basically that's what you have to do, but there are some small additional steps (adapting your host file for example, follow the readme)
103. http://puppetlabs.com/ the whole vm is set up with puppet modules
104. https://github.com/bashofmann/vm_js_mashup
105. http://twitter.com/BastianHofmann http://profiles.google.com/bashofmann http://lanyrd.com/people/BastianHofmann http://speakerdeck.com/u/bastianhofmann https://github.com/bashofmann https://www.researchgate.net/profile/Bastian_Hofmann/ mail@bastianhofmann.de Did you like this talk? http://joind.in/talk/view/8041 thanks, you can contact me on any of these platforms or via mail. if you liked this talk or didn't like it, please rate it on joind.in. this is very important for me for improving my talk, for the organizers for selecting the best talks and speakers and for you to get the best content on the conferences you visit.