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• Using the jQuery wrapper and implicit iteration Understanding these three concepts in detail is foundational when it comes time to write your own jQuery code or augment the recipes found in this book. Let’s examine each of these concepts in detail. Find some elements and do something with them Or more specifically stated, locate a set of elements in the DOM, and then do something with that set of elements. For example, let’s examine a scenario where you want to hide a from the user, load some new text content into the hidden , change an attribute of the selected , and then finally make the hidden visible again. This last sentence translated into jQuery code would look something like this: old content //hide all divs on the page jQuery('div').hide(); //update the text contained inside of all divs jQuery('div').text('new content'); //add a class attribute with a value of updatedContent to all divs jQuery('div').addClass("updatedContent"); //show all divs on the page jQuery('div').show(); Let’s step through these four jQuery statements: • Hide the element on the page so it’s hidden from the user’s view. • Replace the text inside the hidden with some new text (new content). • Update the element with a new attribute (class) and value (updatedContent). • Show the element on the page so it’s visible again to the viewing user. If the jQuery code at this point is mystical syntax to you, that’s OK. We’ll dive into the basics with the first recipe in this chapter. Again, what you need to take away from this code example is the jQuery concept of “find some elements and do something with 4 | Chapter 1: jQuery Basics
them.” In our code example, we found all the elements in the HTML page using the jQuery function (jQuery()), and then using jQuery methods we did something with them (e.g., hide(), text(), addClass(), show()). Chaining jQuery is constructed in a manner that will allow jQuery methods to be chained. For example, why not find an element once and then chain operations onto that element? Our former code example demonstrating the “Find some elements and do something with them” concept could be rewritten to a single JavaScript statement using chaining. This code, using chaining, can be changed from this: to this: //hide all divs on the page jQuery('div').hide(); //update the text contained inside of the div jQuery('div').text('new content'); //add a class attribute with a value of updatedContent to all divs jQuery('div').addClass("updatedContent"); //show all divs on the page jQuery('div').show(); jQuery('div').hide().text('new content').addClass("updatedContent").show(); or, with indenting and line breaks, to this: jQuery('div') .hide() .text('new content') .addClass("updatedContent") .show(); Plainly speaking, chaining simply allows you to apply an endless chain of jQuery methods on the elements that are currently selected (currently wrapped with jQuery functionality) using the jQuery function. Behind the scenes, the elements previously selected before a jQuery method was applied are always returned so that the chain can continue. As you will see in future recipes, plugins are also constructed in this manner (returning wrapped elements) so that using a plugin does not break the chain. If it’s not immediately obvious, and based on the code in question, chaining also cuts down on processing overhead by selecting a set of DOM elements only once, to then be operated on numerous times by jQuery methods by way of chaining. Avoiding unnecessary DOM traversing is a critical part of page performance enhancements. Whenever possible, reuse or cache a set of selected DOM elements. 1.0 Introduction | 5
Page 1 and 2: Solutions & Examples for jQuery Dev
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Page 8 and 9: 2.3 Selecting Elements by Index Ord
Page 10 and 11: 8.5 Passing Dynamic Data to Event H
Page 12 and 13: 16.5 Using HTML Fragments and jQuer
Page 14 and 15: This is largely what makes somethin
Page 16 and 17: on client-side optimization techniq
Page 18 and 19: Tech Editors Karl Swedberg, after h
Page 20 and 21: What You’ll Learn We’ll start o
Page 22 and 23: If none of this works, it’s possi
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Page 26 and 27: traversing and manipulation, browse
Page 30 and 31: The jQuery wrapper set A good major
Page 32 and 33: — Attr — Class — HTML — Tex
Page 34 and 35: alert('jQuery ' + jQuery.fn.jquery)
Page 36 and 37: alert(jQuery('p').text()); }); T
Page 38 and 39: You should be aware that the first
Page 40 and 41: "4 inputs" alert('selected' + jQuer
Page 42 and 43: 1.6 Finding Descendant Elements Wit
Page 44 and 45: .end().end().length); //alerts 3
Page 46 and 47: Now, let’s select the second ele
Page 48 and 49: jQuery('jQuery').find('a').attr('hr
Page 50 and 51: • While the elements selected are
Page 52 and 53: Discussion The cloning method is ac
Page 54 and 55: method by passing the method the at
Page 56 and 57: jQuery('p').text('Hello World,
Page 59 and 60: 2.0 Introduction CHAPTER 2 Selectin
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Page 63 and 64: all siblings that follow, not just
Page 65 and 66: Discussion As mentioned, an element
Page 67 and 68: 2.6 Selecting Elements by What They
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Page 71 and 72: These filters can also be used with
Page 73 and 74: Solution As well as passing a selec
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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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ligula. Aenean mattis pulvinar est
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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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available on the Web. jQuery hosts
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Discussion In the preceding example
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.click(function() { // Special clic
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}); })(jQuery); 4.3 Filtering Array
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Discussion In this example, we have
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}); }); })(jQuery); Discussion Upon
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Discussion In this recipe, we use t
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Solution The if/else statement and
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var foo = new Foo( 'bar' ); foo.ale
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} $('#province').toggle( value == '
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Did jQuery invent chaining? No. jQu
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Whether the idea comes from elsewhe
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}; return object; That could also b
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null or undefined, remove the attri
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The +new Date in this code is just
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(function() { var log = [], index =
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The page also contains a large numb
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you could use this: $('.clientX') /
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And you have this HTML code in your
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when you discover the slow parts, y
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A Warning About for..in Loops Never
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Other code here calls maxMagnitude
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matter, but in performance-critical
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console.log( $foo ); $foo.css({ fon
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Solution 1 You’re using the minif
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After the page loads, you are down
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5.19 Writing Unobtrusive JavaScript
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Documentation Tutorials We’ve
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Beware that you don’t make the us
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+ $(document).scrollLeft() }) .show
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Want to read more? You can find thi
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