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amd.rst

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  1. AMD
    2. 

  2. ###
    3. 

  3. 

  4. .. toctree::
    5. 

  5.    :maxdepth: 2
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  6. 

  7. Overview
    8. 

  8. ========
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  9. 

  10. There are two JavaScript system in Elgg: the deprecated 1.8 system, and the newer `AMD (Asynchronous Module
    11. 

  11. Definition) <http://requirejs.org/docs/whyamd.html>`_ compatible system introduced in 1.9.
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  12. 

  13. This discusses the benefits of using AMD in Elgg.
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  14. 

  15. Why AMD?
    16. 

  16. ========
    17. 

  17. 

  18. We have been working hard to make Elgg's JavaScript more maintainable and useful.
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  19. We made some strides in 1.8 with the introduction of the "``elgg``" JavaScript object and library, but
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  20. have quickly realized the approach we were taking was not scalable.
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  21. 

  22. The size of `JS on the web is growing
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  23. <http://httparchive.org/trends.php?s=All&minlabel=Feb+11+2011&maxlabel=Feb+1+2013#bytesJS&reqJS>`_
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  24. quickly, and JS in Elgg is growing too. We want Elgg to be able to offer a solution that makes JS
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  25. development as productive and maintainable as possible going forward.
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  26. 

  27. The `reasons to choose AMD <http://requirejs.org/docs/whyamd.html>`_ are plenteous and
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  28. well-documented. Let's highlight just a few of the most relevant reasons as they relate to Elgg
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  29. specifically.
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  30. 

  31. 1. Simplified dependency management
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  32. -----------------------------------
    33. 

  33. AMD modules load asynchronously and execute as soon as their dependencies are available, so this
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  34. eliminates the need to specify "priority" and "location" when registering JS libs in Elgg. Also, you
    35. 

  35. don't need to worry about explicitly loading a module's dependencies in PHP. The AMD loader (RequireJS in this
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  36. case) takes care of all that hassle for you. It's also possible have
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  37. `text dependencies <http://requirejs.org/docs/api.html#text>`_ with the RequireJS text plugin,
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  38. so client-side templating should be a breeze.
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  39. 

  40. 2. AMD works in all browsers. Today.
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  41. ------------------------------------
    42. 

  42. Elgg developers are already writing lots of JavaScript. We know you want to write more. We cannot
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  43. accept waiting 5-10 years for a native JS modules solution to be available in all browsers before
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  44. we can organize our JavaScript in a maintainable way.
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  45. 

  46. 3. You do not need a build step to develop in AMD.
    47. 

  47. --------------------------------------------------
    48. 

  48. We like the edit-refresh cycle of web development. We wanted to make sure everyone developing in
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  49. Elgg could continue experiencing that joy. Synchronous module formats like Closure or CommonJS just
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  50. weren't an option for us. But even though AMD doesn't require a build step, *it is still very
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  51. build-friendly*. Because of the ``define()`` wrapper, it's possible to concatenate multiple modules
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  52. into a single file and ship them all at once in a production environment. [#]_
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  53. 

  54. AMD is a battle-tested and well thought out module loading system for the web today. We're very
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  55. thankful for the work that has gone into it, and are excited to offer it as the standard solution
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  56. for JavaScript development in Elgg starting with Elgg 1.9.
    57. 

  57. 

  58. .. [#] This is not currently supported by Elgg core, but we'll be looking into it since reducing round-trips is critical for a good first-view experience, especially on mobile devices.
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  59.