Jquery Performance Optimization Method

I have been searching

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I. selector performance optimization suggestions
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1.
This is

1 $ ('# content'). hide ();

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Or from

2 $ ('# content p'). hide ();

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2.
JQuery

3 varreceiveNewsletter =ter ('# nslForm input. on ');

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In the jQuery browser, it will traverse all

4 varcontent = $ ('div # content ');//

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Use

5 vartraffic_light = $ ('# content # traffic_light ');//

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3.
Cache the parent object for future use

6 varheader = $ ('# header ');

7 varmenu = header. find ('. menu ');

8 //

9 varmenu = $ ('. menu', header );

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4.
Self-version
Var linkContacts = $ ('. contact-links div. side-wrapper ');
Do not use
Var linkContacts = $ ('A. contact-links. side-wrapper ');

5.
. Find ()

10 vardivs = $ ('. testdiv', '# pageBody'); // 2353 on Firebug 3.6

11 vardivs = $ ('# pageBody'). find ('. testdiv'); // 2324 on Firebug 3.6-The best time

12 vardivs = $ ('# pageBody. testdiv'); // 2469 on Firebug 3.6

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6.
Use

13 $ ('Li. menu-item'). click (function () {alert ('test click ');})

14. css ('display', 'block ')

15. css ('color', 'red ')

16 fadeTo (2, 0.7 );

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Remember, never let the same selector appear multiple times in your code:
(

7.
If you often use selector in code, then the extension

17 $. extend ($. expr [':'], {

18 abovethefold: function (el ){

19 return $ (el). offset (). top <$ (window). scrollTop () + $ (window). height ();

20}

21 });

22 varnonVisibleElements = $ ('div: abovethefold ');//

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Ii. Optimization
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8.
Cache frequently used elements:

23 varheader = $ ('# header ');

24 vardivs = header. find ('div ');

25 varforms = header. find ('form ');

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9.
The basic idea here is to create what you really want in the memory and then update
Direct

26 varmenu = '<ul id = "menu"> ';

27 for (vari = 1; I <100; I ++ ){

28 menu + = '<li>' + I + '</li> ';

29}

30 menu + = '</ul> ';

31 $ ('# header'). prepend (menu );

32 //

33 $ ('# header'). prepend (' <ul id = "menu"> </ul> ');

34 for (vari = 1; I <100; I ++ ){

35 $ ('# menu'). append ('<li>' + I + '</li> ');

36}

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Bubble event: unless in special circumstances

37 $ ("# entryform input"). bind ("focus", function (){

38 $ (this). addClass ("selected ");

39}). bind ("blur", function (){

40 $ (this). removeClass ("selected ");

41 });

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Of course, the above Code can help us complete the corresponding tasks, but if you want to find a more efficient method, please use the following code:

42 $ ("# entryform"). bind ("focus", function (e ){

43 var $ cell = (e.tar get); // e.tar get

44 $ cell. addClass ("selected ");

45}). bind ("blur", function (e ){

46 var $ cell = (e.tar get );

47 $ cell. removeClass ("selected ");

48 });

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You can perform operations on the target element by obtaining the focus and losing the focus in the parent listener. In the code above, the parent element plays the role of a dispatcher.

49 $ ('# myTable td'). click (function (){

50 rows (this).css ('background', 'red ');

51 });

52 improvement methods:

53 $ ('# mytable'). click (function (e ){

54 var $ clicked = require (e.tar get );

55 export clicked.css ('background', 'red ');

56 });

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Assume that

10.
Although

11.
For better performance, you should use direct functions such

12.
You often get

57 App. hiddenDivs =$ ('div. Den den ');

58 //

59 App. hiddenDivs. find ('span ');

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13.
Don't forget to use

60 $ ('# head'). data ('name', 'value ');

61 //

62 $ ('# head'). data ('name ');

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14.
Do not forget the simple and practical utility. What I like most is

15.
When
$ ('Html '). addClass ('js ');
Only when enabled
/*
. JS # myDiv {display: none ;}
So when


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Iii. Suggestions on optimizing event Performance
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16.
Sometimes

17.
When you have many nodes in a container, you want to bind an event to all nodes,

63 $ ("table"). delegate ("td", "hover", function (){

64 $ (this). toggleClass ("hover ");

65 });

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18.
If you want to compress

66/

67 $ (document). ready (function (){

68 //

69 });

70 //

71 $ (function (){

72 //

73 });

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Iv. Test
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19. jQuery
Test Selenium, Funcunit, QUit, and QMock to test your code (especially plug-ins ). I want to discuss this topic in another topic because there are too many things to talk about.

20.
You often standardize your code to see which query is slow and then replace it. You can use jQuery to make the test easier:

74 //

75 $. l ($ ('div '));

76 //

77 $. time ();

78 //

79 $. lt ();

80 $ ('div ');

81 $. lt ();

82 //

83 $. bm ("var divs = $ ('. testdiv', '# pageBody');"); // 2353 on Firebug 3.6

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5. Other common
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21.
The latest version is often the best. After changing the version, do not forget to test your code. Sometimes it is not completely backward compatible.

22.
New

23.
The best way to add styles to a few elements is to use

84 $ ('<style type = "text/css"> div. class {color: red ;}</style> ')

85. appendTo ('head ');

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24.
Set

25.
When you have determined which files should be loaded, package them into a file. You can use some open-source tools to automatically compress your files, such as using Minify (JSCompressor, YUI Compressor, or Dean Edwards JS packer. My favorite is JSCompressor.

26.
Use

27.
When your application is officially launched

86 //

87 <script type = "text/javascript" src = "[color = blue! Important] [url = Success "> </script>

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28 .(
Use