Web front-end development jquery Common instance code fragment (50) _jquery

This article shows you 50 pieces of jquery code that can help with your JavaScript project. Some of these pieces of code are supported by jQuery1.4.2 and others are really useful functions or methods that can help you get things done quickly and well. These are the best performance snippets I've ever tried to remember, so if you find anything you can do better, please paste your version in the comments! I hope you can find something helpful in this article.

1. How to create a nested filter

Filters that allow you to reduce the matching elements in the collection,//Only those parts that match the given selector. In this case,//The query removes any (: not) (: has)//contains child nodes with Class "Selected" (. selected). Filter (: Not () has (. selected))

2. How to reuse element search

 var AllItems = $ ("Div.item"); var keeplist = $ ("Div#container1 Div.item"); Now you can continue to work with these jquery objects. For example,///based on the checkbox to crop "Keep list", the check box name//conforms to 
 <div>class names:
 $ (Formtolookat + "input:checked"). each (function () {keeplist = Keeplist.filter ("." + $ (This). attr ("name"))
 ; </DIV>

3. Any use of has () to check whether an element contains a class or element

The JQuery 1.4.* contains support for this has approach. This method finds out//whether an element contains another element class or anything else that you are looking for and operating on. $ ("input"). has (". Email"). AddClass ("Email_icon");

4. How to use jquery to switch style sheets

 Find the type of media you want to switch (Media-type), and then set the href to a new style sheet.
$ (' link[media= ' screen '] '). attr (' href ', ' alternative.css ');

5. How to limit selection (based on optimization purposes)

    Use the tag name as a prefix to the class name whenever possible,     so jquery doesn't need to spend more time searching     //The elements you want. One thing to keep in mind is that the     more specific the operations of the elements on your page are, the     more you can reduce the time to execute and search.
 var in_stock = $ (' #shopping_cart_items input.is_in_stock ');
 <ul id= "Shopping_cart_items" > <li><input type= "Radio" value= "Item-x" name= "Item" class= "Is_in_stock"/ >item x</li> <li><input type= "Radio" value= "Item-y" name= "Item" class= "3-5_days"/>Item Y</li > <li><input type= "Radio" value= "Item-z" name= "Item" class= "Unknown"/>item z</li> </ul>

6. How to use Toggleclass correctly

    The Toggle (toggle) class allows you     to add or remove a class based on whether or not it exists.     //In this case some developers use:
 a.hasclass (' BlueButton ')? A.removeclass (' BlueButton '): A.addclass (' BlueButton ');
Toggleclass allows you to use the following statement to easily do this

a.toggleclass (' BlueButton ');

7. How to set the features of IE specific

  if ($.browser.msie) {
//Internet Explorer is actually less useful

}

8. How to use jquery to replace an element

 $ (' #thatdiv '). ReplaceWith (' Fnuh ');

9. How to verify that an element is empty

  if ($ (' #keks '). html (). Trim ()) {
//nothing found;

}

10. How to find the index number of an element from an unordered collection

 $ ("ul > Li"). Click (function () {var index = $ (this). Prevall (). length;});

11. How to bind functions to events

 $ (' #foo '). Bind (' click ', function () {alert (' User clicked on ' foo. "');});

12. How to append or add HTML to an element

 $ (' #lal '). Append (' Sometext ');

13. How to use object literals (literal) to define attributes when creating elements

 var e = $ ("", {href: "#", Class: "A-class Another-class", Title: "..."});

14. How to use multiple properties to filter

  When using many similar input elements of different types,     //This method based on precision is useful for
   var elements = $ (' #someid input[type=sometype][value=somevalue ]. get ();

15. How to use jquery to preload an image

 Jquery.preloadimages = function () {for (var i = 0; i < arguments.length; i++) {$ (" 
 

16. How to set an event handler for any element that matches the selector

 $ (' Button.someclass '). Live (' click ', someFunction);/note that in the jquery 1.4.2, delegate and undelegate Options//are introduced instead of live, Because they provide better context support//For example, in the case of table, you used to use//.live () $ ("table"). each (function () {$ ("TD", this). Live ("hover", function () {$ (t His). Toggleclass ("hover"); }); )//Now with $ ("table"). Delegate ("TD", "hover", function () {$ (this). Toggleclass ("hover");

17. How to find an option element that has been selected

 $ (' #someElement '). Find (' option:selected ');

18. How to hide an element that contains a text of a value

 $ ("P.value:contains (' Thetextvalue ')"). Hide ();

19. If you scroll to an area of the page automatically

  JQuery.fn.autoscroll = function (selector) {

$ (' html,body '). Animate ({scrolltop: $ (this). Offset (). Top},
500< c3/>);
}
Then scroll like this to the class/area you want to go to.

$ ('. Area_name '). AutoScroll ();

20. How to detect various browsers

 if ($.browser.safari)//Detect Safari
if ($.browser.msie && $.browser.version > 6)//detect IE6 and after version
if ($. Browser.msie && $.browser.version <= 6)//Detect IE6 and previous versions
if ($.browser.mozilla && $. Browser.version >= ' 1.8 ')//Check Firefox 2 and after version

21. How to replace the words in a string

 var el = $ (' #id '); El.html (el.html (). Replace (/word/ig, "));

22. How to disable right-click context menu

$ (document). Bind (' ContextMenu ', function (e) {return

false;
});

23. How to define a custom selector

$.expr[': '].mycustomselector = function (element, index, meta, stack) {//element-the current loop index in a DOM element//index– stack//meta– has The metadata//stack– for the off selector is the stack of all elements to loop//If the current element is included, returns TRUE//returns False if the current element is not included; Custom Selector Usage: $ ('. Someclasses:test '). dosomething ();

24. How to check if an element exists

if ($ (' #someDiv '). Length) {
//Your sister, finally found it.
}

25. How to use jquery to detect two mouse clicks with right and left buttons

 $ ("#someelement"). Live (' click ', Function (e) {if (!$.browser.msie && e.button = 0) | | ($.browser.msie && E.button = 1)) {alert ("Left Mouse button clicked");} else if (E.button = = 2) {alert ("Right Mouse button clicked");});

26. How to display or delete the default values in the input field

This code shows     how to keep//a default value of $ (". Swap") in the input field of the text type when the user does not enter     a value
 . Each (function (i) {wap_val[i] = $ (this). Val ( ); $ (this). Focusin (function () {if ($ (this). val () = = Swap_val[i]) {$ (this). Val ("");}). Focusout (function () {if ($.trim ($ (this). val ()) = = "") {$ (this). Val (Swap_val[i]);}});

27. How to automatically hide or close elements after a period of time (support version 1.4)

This is the way we use settimeout to implement in 1.3.2
 settimeout (function () {$ ('. Mydiv '). Hide (' blind ', {}, 500)}, 5000); This is the way that you can use the delay () feature in 1.4 (which is much like hibernation) $ (". Mydiv"). Delay (5000). Hide (' blind ', {}, 500);

28. How to dynamically add elements that have been created to the DOM

var newdiv = $ (");
NEWDIV.ATTR (' id ', ' mynewdiv '). Appendto (' body ');

29. How to limit the number of characters in the "Text-area" field

 JQuery.fn.maxLength = function (max) {This.each (function () {var type = This.tagName.toLowerCase (); var inputtype = this . type? This.type.toLowerCase (): null; if (type = = "Input" && inputtype = = "Text" | | | inputtype = = "Password") {this.maxlength = max;} else if (type = = "TextArea") {this.onkeypress = function (e) {var ob = e | | event; var keycode = Ob.keycode; var hasselection = document. Selection? Document.selection.createRange (). text.length > 0:this.selectionstart!= this.selectionend; Return! (This.value.length >= Max && (KeyCode > | | keycode = | | keycode = 0 | | keycode =) &&!ob . Ctrlkey &&!ob.altkey &&!hasselection); }; This.onkeyup = function () {if (This.value.length > Max) {this.value = this.value.substring (0, Max);}}; } }); };
Usage $ (' #mytextarea '). MaxLength (500);

30. How to create a basic test for a function

Separate the tests into modules ("Module B"); Test ("Some other test", function () {//Indicates how many assertions expect (2) are expected to run within the test);//A comparison assertion, equivalent to JUnit's assertequals equals (true, false, " Failing test "); Equals (True, true, "passing Test"); });

31. How to clone an element in jquery

var cloned = $ (' #somediv '). Clone ();

32. How to test whether an element is visible in jquery

  if ($ (Element). Is (': Visible ')) {
//The element is visible
}

33. How to place an element in the center of the screen

 JQuery.fn.center = function () {this.css (' position ', ' absolute '); This.css (' Top ', ($ window). Height ()-this.height ()) c9/>/+$ (window). scrolltop () + ' px '); This.css (' Left ', ($ (window). Width ()-this.width ()) 
 /2 + $ (window). ScrollLeft () + ' px ');

34. How to put the values of all elements that have a particular name in an array

var arrinputvalues = new Array ();
$ ("Input[name= ' table[]"). each (function () {
Arrinputvalues.push ($ (this). Val ());
});

35. How to remove HTML from an element

(function ($) {$.fn.striphtml = function () {var regexp =/< ("[^"]* "|") [^']*'| [^ ' "]) *>/gi; This.each (function () {$ (this). HTML ($ (this). html (). Replace (RegExp, "")); return $ (this); }) (JQuery);

36. How to use closest to get the parent element

 $ (' #searchBox '). Closest (' div ');

37. How to use Firebug and Firefox to record jquery event logs

Allow chained logging//Usage: $ (' #someDiv '). Hide (). log (' div hidden '). addclass (' SomeClass '); JQuery.log = JQuery.fn.log = function (msg) {if (console) {Console.log ("%s:%o", MSG, this);} return this; };

38. How to force a link to open in a pop-up window

JQuery (' A.popup '). Live (' click '), function () {NewWindow = window.open ($ (this). attr (' href '), ', ' height=200,width=150 ' ); if (window.focus) {Newwindow.focus ();} return false; });

39. How to force a link to open in a new tab

 jquery (' A.newtab '). Live (' click ', Function () {NewWindow = window.open ($ (this). href); JQuery (this). target = "_blank"; return false; });

40. How to use. Siblings () in jquery to select sibling elements

  Do not do so
 $ (' #nav li '). Click (function () {$ (' #nav Li '). Removeclass (' active '); $ (this). addclass (' active ');});
The alternative is
 $ (' #nav li '). Click (function () {$ (this). addclass (' active '). Siblings (). Removeclass (' active ');})

41. How to toggle all check boxes on the page

 var tog = false;
Or True if they are selected at load time
 $ (' a '). Click (function () {$ ("Input[type=checkbox]"). attr ("Checked",!tog); tog =!tog ; });

42. How to filter a list of elements based on some input text

If the value of the element matches the input text     //The element will be returned
 $ ('. SomeClass '). Filter (function () {return $ (this). attr (' value ') = = $ (' Input#someid '). Val (); })

43. How to get mouse pad cursor position x and Y

$ (document). Ready (function () {$ (document). MouseMove (function (e) {$ (' #XY '). HTML ("X Axis: + E.pagex +" | Y Axis "+ e.pagey);}";

44. How to turn the entire list element (Element,li) into a clickable

$ ("ul Li"). Click (function () {window.location = $ (this). Find ("a"). attr ("href");
 <ul> <li><a href= "#" >link 1</a></li> <li><a href= "#" >link 2</a></ Li> <li><a href= "#" >link 3</a></li> <li><a href= "#" >Link 4</a></li > </ul>

45. How to use jquery to parse XML (basic example)

function Parsexml (XML) {//finds each Tutorial and prints out author $ (XML). Find ("Tutorial"). each (function () {$ ("#output"). Append ( This). attr ("author") + "");}

46. How to check if the image has been fully loaded in

$ (' #theImage '). attr (' src ', ' image.jpg '). Load (function () {alert (' This image has Been Loaded ');});

47. How to use jquery to specify namespaces for events

Events can thus bind the namespace $ (' input '). Bind (' Blur.validation ', function (e) {//...}); The data method also accepts the namespace $ (' input '). Data (' Validation.isvalid ', true);

48. How to check whether cookies are enabled

var dt = new Date (); Dt.setseconds (Dt.getseconds () + 60); Document.cookie = "cookietest=1; Expires= "+ dt.togmtstring (); var cookiesenabled = document.cookie.indexOf ("cookietest=")!=-1; if (!cookiesenabled) {//No cookies enabled}

49. How to make cookies expire

var date = new Date (); Date.settime (Date.gettime () + (x * 60 * 1000)); $.cookie (' Example ', ' foo ', {expires:date});

50. How to use a clickable link to replace any URL in the page

 $.fn.replaceurl = function () {var regexp =/(FTP|HTTP|HTTPS): \/\/(\w+:{0,1}\w*@)? ( \s+) (: [0-9]+)? (\/|\/([\w#!:.? +=&%@!\-\/])? /gi; This.each (function () {$ (this). HTML ($ (this). html (). Replace (RegExp, ' <a href= ' >$1</a>);}); return $ (this); }
//Usage $ (' P '). Replaceurl ();

The above content is to introduce the Web front-end development jquery Common example code fragment (50), I hope you like.