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Contextual jQuery in Practice

Doug Neiner
October 02, 2011

Contextual jQuery in Practice

Building on the principles taught last year in my session titled "Contextual jQuery" (See http://bit.ly/contextualjquery for a video), we'll take off the kid gloves and dive into the techniques you will need to write adaptive, reusable and responsible jQuery.

Doug Neiner

October 02, 2011
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  1. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER JQUERY CODE STYLES •

    Declarative • Large number of selectors running on document ready • Id-centric selections • Traditional Event Binding • Dynamic • Large number of selectors running on document ready • Class-centric selections • Mix of traditional event binding with some delegated events
  2. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER JQUERY CODE STYLES •

    Contextual • Very few selectors run on document ready • Context-centric traversing and filtering • Heavy use of delegated events with some traditional binding
  3. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER WRITE CODE LIKE YOU

    SPEND MONEY Opt to pay a little more later so you don’t risk losing it all on something that never happens
  4. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER WRITE CODE LIKE YOU

    BUY A CAR Always weigh the difference between cost and quality
  5. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER OVERVIEW • Understanding the

    power of delegated events • Detecting probable user behavior • Automatic Initialization with Deferreds • Predicting user behavior with localStorage
  6. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER UNDERSTANDING DELEGATION click click

    click click click click click click click click click click CONTAINER CONTAINER $( "#tile a" ) .bind( "click", … ); $( "#tile" ) .delegate( "a", "click", … ); $( "#tile" ) .on( "click", "a", … );
  7. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER UNDERSTANDING DELEGATION • Event

    bubbling allows it to work (This is patched by jQuery as necessary) • One event on a parent vs. many events on children • Filtering vs. Traversal • Responsible events – only run on user action • Can be added before the document is ready • Forces a contextual approach
  8. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER ONE TIME INITIALIZATION PATTERN

    $( document ) ! .delegate( "li:not(.widget-setup)", "click", function () { ! ! // Do something here ! ! $( this ).addClass( "widget-setup" ); ! });
  9. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER CLICK • Action is

    definite • Often too late to avoid delays • Great for actions not requiring remote requests • Loading indicators will probably be needed
  10. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER MOUSEENTER / MOUSELEAVE •

    Action has a high probability • More expensive to listen for • Many false positives • Great for drag and drop initialization
  11. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER MOUSEENTER / MOUSELEAVE //

    Old Way $( document ).ready( function() { // 1000 item iteration, woah! $( "div.item" ).draggable(); }); // With Delegate $( document ) ! .delegate( "div.item:not( .ui-draggable )", "mouseenter", ! ! function ( e ) { // Only ended up running on 15 items $( this ).draggable({ … }); ! ! } ! );
  12. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER MOUSE ENTER/LEAVE & DOTIMEOUT

    • jQuery.doTimeout is a plugin by Ben Alman: http://bit.ly/dotimeout • Action has a very high probability • May require a click safety net for fast movers • Fewer false positives
  13. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER MOUSE ENTER/LEAVE & DOTIMEOUT

    function initializeSocialWidgets() { ! // Run setup here } $( document ) ! .delegate( "article", "mouseenter mouseleave", ! ! function ( e ) { ! ! ! var $el = $( this ); ! ! ! ! ! if ( e.type === "mouseenter" ) { ! ! ! ! $el.doTimeout( "social", 500, ! ! ! ! ! $.proxy( initializeSocialWidgets, $el ) ! ! ! ! ); ! ! ! } else { ! ! ! ! $el.doTimeout( "social" ); ! ! ! } ! ! } ! );
  14. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER MOUSE ENTER/LEAVE & DOTIMEOUT

    $( document ) ! .delegate( "article", "mouseenter mouseleave click", ! ! function ( e ) { ! ! ! var $el = $( this ); ! ! ! ! ! if ( e.type === "mouseenter" ) { ! ! ! ! $el.doTimeout( "social", 500, ! ! ! ! ! $.proxy( initializeSocialWidgets, $el ) ! ! ! ! ); ! ! ! } else if ( e.type === "mouseenter" ) { ! ! ! ! $el.doTimeout( "social" ); ! ! ! } else { ! ! ! ! $el.doTimeout( "social", false ); ! ! ! } ! ! } ! );
  15. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER SCROLLING • Action has

    a medium probability, but easy to detect when an action cannot happen • Could be expensive, try to use cached data • jQuery Waypoints: http://bit.ly/jquerywaypoints • jQuery Sonar: http://bit.ly/jquerysonar • Ideas • Initialize tabs widget in footer • Run markup changes on articles before they come into view
  16. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER FOCUS • Action has

    high probability • Great time to initialize something like autocomplete, a date picker, or validation on a form • Remember: focusin and focusout • Ideas: • Load the rest of a multi-step wizard • Load assets for the web app after focus on a signup form
  17. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER SETUP CODE var contactPopover

    = ( function () { ! var contact_form; // Private variable ! ! return function () { ! ! if ( contact_form ) { ! ! ! return contact_form; ! ! } else { ! ! ! var dfd = $.Deferred(); ! ! ! $.get( '/contact', function ( data ) { ! ! ! ! contact_form = $( data ).hide().appendTo( document.body ); ! ! ! ! dfd.resolve( contact_form ); ! ! ! }); ! ! ! return dfd.promise(); ! ! } ! }; }());
  18. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER SETUP CODE var contactPopover

    = ( function () { ! var contact_form; // Private variable ! ! return function () { ! ! if ( contact_form ) { ! ! ! return contact_form; ! ! } else { ! ! ! var dfd = $.Deferred(); ! ! ! $.get( '/contact', function ( data ) { ! ! ! ! contact_form = $( data ).hide().appendTo( document.body ); ! ! ! ! dfd.resolve( contact_form ); ! ! ! }); ! ! ! return dfd.promise(); ! ! } ! }; }());
  19. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER SETUP CODE var contactPopover

    = ( function () { ! var contact_form; // Private variable ! ! return function () { ! ! if ( contact_form ) { ! ! ! return contact_form; ! ! } else { ! ! ! var dfd = contact_form = $.Deferred(); ! ! ! $.get( '/contact', function ( data ) { ! ! ! ! contact_form = $( data ).hide().appendTo( document.body ); ! ! ! ! dfd.resolve( contact_form ); ! ! ! }); ! ! ! return dfd.promise(); ! ! } ! }; }());
  20. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER SETUP CODE var contactPopover

    = ( function () { ! var contact_form; // Private variable ! ! return function () { ! ! if ( contact_form ) { ! ! ! return contact_form; ! ! } else { ! ! ! var dfd = $.Deferred(); ! ! ! $.get( '/contact', function ( data ) { ! ! ! ! contact_form = $( data ).hide().appendTo( document.body ); ! ! ! ! dfd.resolve( contact_form ); ! ! ! }); ! ! ! return dfd.promise(); ! ! } ! }; }());
  21. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER SETUP CODE var contactPopover

    = ( function () { ! var contact_form; // Private variable ! ! return function () { ! ! if ( contact_form ) { ! ! ! return contact_form; ! ! } else { ! ! ! var dfd = $.Deferred(); ! ! ! $.get( '/contact', function ( data ) { ! ! ! ! contact_form = $( data ).hide().appendTo( document.body ); ! ! ! ! dfd.resolve( contact_form ); ! ! ! }); ! ! ! return dfd.promise(); ! ! } ! }; }());
  22. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER USE CODE // Immediate

    Use $.when( contactPopover() ).then( function ( $popover ) { $popover.show(); }); // Anticipated Use $( document ).delegate( ".contact:not(.init)", "mouseenter", function() { ! $( this ).addClass( "init" ); ! contactPopover(); } );
  23. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER ADVANCED USE // Show

    loader after 0.5 seconds $.doTimeout( "contact", 500, showLoader ); $.when( contactPopover() ).then( function ( $popover ) { // Cancel showing loader or hide if showing $.doTimeout( "contact" ); hideLoader(); $popover.show(); });
  24. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER BENEFITS • You can

    write your action code without a concern for the initialization status • All setup happens in one easy place • Can be triggered at any time to begin initialization
  25. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER TRACKING USER ACTIONS •

    Store a small number of metrics as a user browses your site or application • Keep the information general – don't go overboard • Read this information on page load and respond accordingly • Amplify.store http://amplifyjs.com
  26. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER LOGIN / APP PRELOADING

    // On the final step of signup, // or inside your web application amplify.store( "member", true ); // On the home page if ( amplify.store( "member" ) ) { // Load login popover loadLoginPopover(); // Preload web application assets loadAppAssets(); }
  27. CONTEXTUAL JQUERY IN PRACTICE DOUG NEINER LESS USED ACTIONS //

    On the advanced Edit page or method var timesLoaded = amplify.store( "advancedEdit" ) || 0; timesLoaded += 1; amplify.store( "advancedEdit", timesLoaded ); // On the base page or init method of the app if ( amplify.store( "advancedEdit" ) > 3 ) { ! // Preload advancedEdit ! preoloadAdvanvedEdit(); }