Asynchronous Web Interfaces

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@maccman July 2012 Asynchronous User Interfaces

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What makes design?

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Interaction is fundament to design

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What makes interaction

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Speed is fundamental to interaction

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• Amazon: 100 ms of extra load time caused a 1% drop in sales • Google: 500 ms of extra load time caused 20% fewer searches • Yahoo!: 400 ms of extra load time caused a 5–9% increase in the number of people who clicked “back” before the page even loaded

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It’s not speed, it’s perceived speed

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Network is always a bottleneck

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So why would you tie your interface to your network connection?

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Because it’s easy.

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But it’s not sufﬁcient

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Asynchronous user interfaces are non blocking

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Asynchronous UIs do not wait, they lie

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Lies are all around us

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Why would you optimize for failure?

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Designing an Asyncronous UI

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$('body').dropArea(); $('body').bind('drop', function(e){ e.preventDefault(); e = e.originalEvent; var files = e.dataTransfer.files; for (var i=0; i < files.length; i++) { // Only upload images if (/image/.test(files[i].type)) { createAttachment(files[i]); } }; });

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Secret sauce is generating client side GUIDs

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var createAttachment = function(file) { var uid = [App.username, (new Date).getTime(), 'raw'].join('-'); var data = new FormData(); data.append('attachment[file]', file); data.append('attachment[uid]', uid); $.ajax({ url: '/attachments', data: data, cache: false, contentType: false, processData: false, type: 'POST', }) };

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Instant feedback

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var absText = '![' file.name + '](/attachments/' + uid + ')'; $('.edit').insertAtCaret(absText);

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Parts to an Async UI: • Render on the client • Store state & data on the client • Communicate with the server asynchronously

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Rendering on the client is easy and fast

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Mustache Underscore nano Hogan milk jquery.tmpl EJS dust.js doT.js jaml icanhaz jade pure Handlebars.js Eco

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app/assets/javascripts/views/users.jst.eco

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First name: <%= @firstName %> app/assets/javascripts/views/users.jst.eco

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window.JST['views/users']({firstName: 'User Name'})

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http://styloapp.com

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requestAnimationFrame()

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Batch up DOM updates

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Catapult

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$ catapult new myapp create myapp create myapp/assets/javascripts/app.js create myapp/assets/stylesheets/app.css create myapp/browser.json create myapp/public/index.htm $ cd myapp

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$ catapult server $ catapult build $ catapult watch

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//= require jquery //= require_tree ./app

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Storing state and data on the client

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MVC = Backbone / Spine / Ember

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Store state in the controllers

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Store data in the models

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Preload data

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{ users: [ { name: "Johnny", assets: [ { name: "A file" }, ... ] }, ... ] }

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Validate everything on the client

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validate: function(){ if ( !this.name ) return 'name required'; if ( isNaN(parseInt(this.amount, 10)) ) return 'amount is invalid'; };

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Asynchronous server communication

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Chat example http://spainjs.herokuapp.com/

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Chat example http://spainjs.herokuapp.com/ Source https://gist.github.com/3061694

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$.post('/', {msg: value}, function(){ addMessage({data: value}); });

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$.post('/', {msg: value}); addMessage({data: value});

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get '/stream', :provides => 'text/event-stream' do stream :keep_open do |out| streams << out out.callback { streams.delete(out) } end end post '/' do msg = params[:msg] streams.each do |out| out << "data: #{msg}\n\n" end 204 end

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var es = new EventSource('/stream'); es.onmessage = function(e) { addMessage(e.data); };

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What Spine & Backbone give you

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• CIDs • Async model API • Serial Ajax requests

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model.save();

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model.save(null, {wait: true});

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render: function(){ model.bind('change', function(){ this.$el.html(template(model)) }.bind(this)); }, update: function(){ model.save({ name: this.$name.val() }); },

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While requests are still pending

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window.onbeforeunload = function(){ if (jQuery.active) return 'Are you sure you want to exit?'; };

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When the server fails

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Quick recap

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1. Lie 2. Cheat 3. Steal

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• Don’t block the interface • Async network requests • Store state on the client • Render views on the client • Intelligently preload data

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Thank you! @maccman http://blog.alexmaccaw.com