Thủ thuật lập trình jQuery - phần 2

Sau đây mình sẽ giới thiệu một số lưu ý hy vọng sẽ giúp ích các bạn khi lập trình với Jquery

1. Tạo nhiều filter trên cùng một dòng: 

//a filter allows you to reduce the set of matched elements //to those that match a given selector. In this case the query //removes anything which doesn't (:not) have (:has) a child with //class "selected" (.selected) .filter(":not(:has(.selected))") 

2. Reuse Your Element Searches 

var allItems = $("div.item"); var keepList = $("div#container1 div.item"); //Now you can keep working with those jQuery objects. For example, //trim down the "keep list" based on checkboxes whose names //correspond to <div>class names: $(formToLookAt + " input:checked").each(function() { keepList = keepList.filter("." + $(this).attr("name")); });</div> 

3. Kiểm tra nếu có element hoặc class với lệnh has(): 

//jQuery 1.4.* includes support for the has method. This method will find //if a an element contains a certain other element class or whatever it is //you are looking for and do anything you want to them. $("input").has(".email").addClass("email_icon"); 

4. Đổi CSS với jquery: 

//Look for the media-type you wish to switch then set the href to your new style sheet $('link[media='screen']').attr('href', 'Alternative.css'); 

5. Limit the Scope of Selection (For Optimization): 

//Where possible, pre-fix your class names with a tag name //so that jQuery doesn't have to spend more time searching //for the element you're after. Also remember that anything //you can do to be more specific about where the element is //on your page will cut down on execution/search times var in_stock = $('#shopping_cart_items input.is_in_stock'); <ul id="shopping_cart_items"> <li> <input value="Item-X" name="item" class="is_in_stock" type="radio"> Item X</li> <li> <input value="Item-Y" name="item" class="3-5_days" type="radio"> Item Y</li> <li> <input value="Item-Z" name="item" class="unknown" type="radio"> Item Z</li> </ul> 

6. Correctly Use ToggleClass: 

//Toggle class allows you to add or remove a class //from an element depending on the presence of that //class. Where some developers would use: a.hasClass('blueButton') ? a.removeClass('blueButton') : a.addClass('blueButton'); //toggleClass allows you to easily do this using a.toggleClass('blueButton'); 

7. Thiết lập các hàm dành riêng cho IE: 

if ($.browser.msie) { // Internet Explorer is a sadist. } 
Thay thế một element với Jquery: 

$('#thatdiv').replaceWith('fnuh'); 
Kiểm tra một element rỗng hay không: 

if ($('#keks').html()) { //Nothing found ;} 
Find out the index of an element in an unordered set 

$("ul > li").click(function () { var index = $(this).prevAll().length; }); 
Bind a function to an event: 

$('#foo').bind('click', function() { alert('User clicked on "foo."'); }); 
Append or add HTML to an element: 

$('#lal').append('sometext'); 
Use an object literal to define properties when creating an element 

var e = $("", { href: "#", class: "a-class another-class", title: "..." }); 

8. Filter using multiple-attributes 

//This precision-based approached can be useful when you use //lots of similar input elements which have different types var elements = $('#someid input[type=sometype][value=somevalue]').get(); 

9. Preload images with jQuery: 

jQuery.preloadImages = function() { for(var i = 0; i').attr('src', arguments); } }; // Usage $.preloadImages('image1.gif', '/path/to/image2.png', 'some/image3.jpg');
Set an event handler for any element that matches a selector:

$('button.someClass').live('click', someFunction); //Note that in jQuery 1.4.2, the delegate and undelegate options have been //introduced to replace live as they offer better support for context //For example, in terms of a table where before you would use.. // .live() $("table").each(function(){ $("td", this).live("hover", function(){ $(this).toggleClass("hover"); }); }); //Now use.. $("table").delegate("td", "hover", function(){ $(this).toggleClass("hover"); });

10. Find an option element that’s been selected:
$('#someElement').find('option:selected');

11. Hide an element that contains text of a certain value:
$("p.value:contains('thetextvalue')").hide();

12. AutoScroll to a section of your page:

jQuery.fn.autoscroll = function(selector) { $('html,body').animate( {scrollTop: $(selector).offset().top}, 500 ); } //Then to scroll to the class/area you wish to get to like this: $('.area_name').autoscroll();

13. Disable right-click contextual menu :

$(document).bind('contextmenu',function(e){ return false; });
Define a Custom Selector

$.expr[':'].mycustomselector = function(element, index, meta, stack){ // element- is a DOM element // index - the current loop index in stack // meta - meta data about your selector // stack - stack of all elements to loop // Return true to include current element // Return false to explude current element }; // Custom Selector usage: $('.someClasses:test').doSomething();

14. Check if an element exists
if ($('#someDiv').length) {//hooray!!! it exists...}

15. Detect Both Right & Left Mouse-clicks with jQuery:

$("#someelement").live('click', function(e) { if( (!$.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"); });

16. Show or Erase a Default Value In An Input Field:

//This snippet will show you how to keep a default value //in a text input field for when a user hasn't entered in //a value to replace it swap_val = []; $(".swap").each(function(i){ swap_val = $(this).val(); $(this).focusin(function(){ if ($(this).val() == swap_val) { $(this).val(""); } }).focusout(function(){ if ($.trim($(this).val()) == "") { $(this).val(swap_val); } }); });

17. Automatically Hide or Close Elements After An Amount Of Time (supports 1.4):

//Here's how we used to do it in 1.3.2 using setTimeout setTimeout(function() { $('.mydiv').hide('blind', {}, 500) }, 5000); //And here's how you can do it with 1.4 using the delay() feature (this is a lot like sleep) $(".mydiv").delay(5000).hide('blind', {}, 500);

18. Add Dynamically Created Elements to the DOM:
var newDiv = $(''); newDiv.attr('id','myNewDiv').appendTo('body');

19. Limit The Number Of Characters in a "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"){ //Apply the standard maxLength 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 > 50 || keyCode == 32 || keyCode == 0 || keyCode == 13) && !ob.ctrlKey && !ob.altKey && !hasSelection); }; this.onkeyup = function(){ if(this.value.length > max){ this.value = this.value.substring(0,max); } }; } }); }; //Usage: $('#mytextarea').maxLength(500);

20. Create a basic test for a function:

//Separate tests into modules. module("Module B"); test("some other test", function() { //Specify how many assertions are expected to run within a test. expect(2); //A comparison assertion, equivalent to JUnit's assertEquals. equals( true, false, "failing test" ); equals( true, true, "passing test" ); });

21. Clone an element in jQuery:

var cloned = $('#somediv').clone();
Test if an element is visible in jQuery:

if($(element).is(':visible') == 'true') { //The element is Visible }

22. Center an element on screen:

jQuery.fn.center = function () { this.css('position','absolute'); this.css('top', ( $(window).height() - this.height() ) / +$(window).scrollTop() + 'px'); this.css('left', ( $(window).width() - this.width() ) / 2+$(window).scrollLeft() + 'px');return this;} //Use the above function as: $(element).center();

23. Put the values of all the elements of a particular name into an array:

var arrInputValues = new Array(); $("input[name='table[]']").each(function(){ arrInputValues.push($(this).val()); });

24. Strip HTML From Your Element

(function($) { $.fn.stripHtml = function() { var regexp = /<("[^"]*"|'[^']*'|[^'">])*>/gi; this.each(function() { $(this).html( $(this).html().replace(regexp,”") ); }); return $(this); } })(jQuery); //usage: $('p').stripHtml();

25. Get a parent element using closest:
$('#searchBox').closest('div');


26. Log jQuery events using Firebug and Firefox:

// Allows chainable 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; };

27. Force links 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; });

28. Force links to open in a new tab:

jQuery('a.newTab').live('click', function(){ newwindow=window.open($(this).href); jQuery(this).target = "_blank"; return false; });

29. Select siblings in jQuery using .siblings()

// Rather than doing this $('#nav li').click(function(){ $('#nav li').removeClass('active'); $(this).addClass('active'); }); // Do this instead $('#nav li').click(function(){ $(this).addClass('active') .siblings().removeClass('active'); });

30. Toggle All the checkboxes on a page:

var tog = false; // or true if they are checked on load $('a').click(function() { $("input[type=checkbox]").attr("checked",!tog); tog = !tog; });

31. Filter down a list of elements based on some input text:

//If the value of the element matches that of the entered text //it will be returned $('.someClass').filter(function() { return $(this).attr('value') == $('input#someId').val() ; })

32. Get mouse cursor X and Y

$(document).mousemove(function(e){ $(document).ready(function() { $().mousemove(function(e){ $("#XY").html("X Axis : " + e.pageX + " | Y Axis " + e.pageY); }); });

33. Make an entire List Element (LI) clickable

$("ul li").click(function(){ window.location=$(this).find("a").attr("href"); return false; }); <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>

34. Parse XML with jQuery (Basic example):

function parseXML(XML) { //find every Tutorial and print the author $(XML).find("Tutorial").each(function() { $("#output").append($(this).attr("author") + ""); }); }

35. Check if an image has been fully loaded:

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

36. How to namespace events using jQuery:

//Events can be namespaced like this $('input').bind('blur.validation', function(e){ // ... }); //The data method also accept namespaces $('input').data('validation.isValid', true);

37. Check if Cookies Are Enabled Or Not:

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) { //cookies have not been enabled }

38. How to Expire A Cookie:

var date = new Date(); date.setTime(date.getTime() + (x * 60 * 1000)); $.cookie('example', 'foo', { expires: date });

39. Replace any URL on your page with a clickable link

$.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">$1</a>‘) ); }); return $(this); } //usage $('p').replaceUrl();