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After the page loads, you are downloading some JSON data using $.getJSON(), thus adding yet another server request: $(document).ready( function() { $.getJSON( 'myjson.php?q=test', function( json ) { $('#demo').html( json.foo ); }); }); myjson.php is a script on your server that returns JSON data like this: { } Solution "foo": "bar" Load jQuery from Google’s Ajax library, and combine all your plugins into a single file: Or, combine all of the JavaScript code you use most frequently (jQuery, plugins, and your own code) into a single file: Either way, it also helps to minify the .js files (remove comments and extra whitespace) to reduce their size. And make sure your server is using gzip compression on the files it downloads. For the JSON data, since this page is generated by your own server application, you can “burn” the JSON data directly into the HTML page as it’s generated, using a tag: var myJson = { "foo": "bar" }; The highlighted portion of that script tag is identical to the JSON data downloaded by myjson.php in the original code. In most server languages it should be easy to include the content in this way. Now the jQuery code to use the JSON data is simply: $(document).ready( function() { $('#demo').html( myJson.foo ); }); 124 | Chapter 5: Faster, Simpler, More Fun
This eliminates one more server request. Discussion One of the keys to fast page loading is to simply minimize the number of HTTP requests. Making requests to different servers can also help. Browsers will make only a small number of simultaneous downloads from any single domain (or subdomain), but if you download some of your files from a different domain, the browser may download them in parallel as well. Pointing different tags to different domains may allow them to be downloaded in parallel, but it doesn’t affect the order of execution. tags are executed in the order they appear in the HTML source. You can combine JavaScript files by hand by simply copying and pasting them into one big file. This is inconvenient for development but does speed up downloading. There are a number of file combiner/minifiers available for various server languages. Ruby on Rails: • Bundle-fu • AssetPackager • The packager built into Rails 2.0 PHP: • Minify Python: • JSCompile Java: • YUI Compressor In addition to JavaScript code, check your CSS for multiple .css files. Some of the tools listed can merge your .css files into a single download, just as they do for .js files. At one time, “packing” JavaScript was all the rage. This not only removes comments and whitespace but also rewrites all of the JavaScript code so that it’s not even JavaScript code anymore. Packing requires an unpacking step at runtime—every time the page loads, even if the Java- Script code is already cached. Because of this, packing has fallen out of favor, and “minifying” the code (removing comments and whitespace) is recommended instead, combined with gzip compression. Much of the benefit of packing comes from removing duplicate strings, and gzip does that for you anyway. 5.18 Making Fewer Server Requests | 125
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Solutions & Examples for jQuery Dev
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jQuery Cookbook
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jQuery Cookbook by jQuery Community
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2.3 Selecting Elements by Index Ord
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8.5 Passing Dynamic Data to Event H
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16.5 Using HTML Fragments and jQuer
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This is largely what makes somethin
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on client-side optimization techniq
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Tech Editors Karl Swedberg, after h
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What You’ll Learn We’ll start o
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If none of this works, it’s possi
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800-998-9938 (in the United States
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traversing and manipulation, browse
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• Using the jQuery wrapper and im
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The jQuery wrapper set A good major
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— Attr — Class — HTML — Tex
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alert('jQuery ' + jQuery.fn.jquery)
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alert(jQuery('p').text()); }); T
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You should be aware that the first
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"4 inputs" alert('selected' + jQuer
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1.6 Finding Descendant Elements Wit
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.end().end().length); //alerts 3
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Now, let’s select the second ele
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jQuery('jQuery').find('a').attr('hr
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• While the elements selected are
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Discussion The cloning method is ac
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method by passing the method the at
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jQuery('p').text('Hello World,
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2.0 Introduction CHAPTER 2 Selectin
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It’s worth noting that combinator
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all siblings that follow, not just
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Discussion As mentioned, an element
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2.6 Selecting Elements by What They
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The preceding selector would select
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These filters can also be used with
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Solution As well as passing a selec
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The purpose of the selector would b
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alert(urls.join(",")); We were able
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Even though this may be the most ob
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Figure 3-2. Code output As you can
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Chapter 3 - Recipe 3 - Converting a
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Figure 3-4. Code output 3.4 Getting
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Discussion The core method index()
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Figure 3-6. Code output In the prec
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Solution Let’s say you inherit a
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If you use this technique, you will
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Page 100 and 101: Discussion In the preceding example
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Page 108 and 109: }); }); })(jQuery); Discussion Upon
Page 110 and 111: Discussion In this recipe, we use t
Page 112 and 113: Solution The if/else statement and
Page 114 and 115: var foo = new Foo( 'bar' ); foo.ale
Page 116 and 117: } $('#province').toggle( value == '
Page 118 and 119: Did jQuery invent chaining? No. jQu
Page 120 and 121: Whether the idea comes from elsewhe
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Page 124 and 125: null or undefined, remove the attri
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Page 132 and 133: you could use this: $('.clientX') /
Page 134 and 135: And you have this HTML code in your
Page 136 and 137: when you discover the slow parts, y
Page 138 and 139: A Warning About for..in Loops Never
Page 140 and 141: Other code here calls maxMagnitude
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Page 144 and 145: console.log( $foo ); $foo.css({ fon
Page 146 and 147: Solution 1 You’re using the minif
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Page 152 and 153: Documentation Tutorials We’ve
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Page 156 and 157: + $(document).scrollLeft() }) .show
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