30 classic jQuery code development tips

This article summarizes 30 classic jQuery code development tips with examples. Share with you for your reference. The details are as follows:

1. Create a nested filter

.filter(":not(:has(.selected))") // Remove all not included class for .selected The elements of the 

Reuse your element queries

var allItems = $("div.item");

var keepList = $("div#container1 div.item");

<div>class names: $(formToLookAt + " input:checked").each(function() { keepListkeepList = keepList.filter("." + $(this).attr("name"));

});

</div>

3. Use has() to determine whether an element contains a specific class or element

//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. Use jQuery to switch styles

//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');

Limit the areas you choose

//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" type="radio"> Item X</li>

<li> <input value="Item-Y" name="item" type="radio"> Item Y</li>

<li> <input value="Item-Z" name="item" type="radio"> Item Z</li>

</ul>

6. How to use ToggleClass correctly

//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 usinga.toggleClass('blueButton');

7. Set the function specified by IE

if ($.browser.msie) { 

// Internet Explorer is a sadist.

}

Replace an element with jQuery

$('#thatdiv').replaceWith('fnuh');

Verify that an element is empty

if ($('#keks').html()) {

//Nothing found ;

}

10. Find 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."'); });

12. Add HTML to an element

$('#lal').append('sometext');

13. Use objects to define attributes when creating elements

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

Use filters to filter 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();

15. Preload images with jQuery

jQuery.preloadImages = function() { for(var i = 0; i').attr('src', arguments[i]); } }; 

// Usage $.preloadImages('image1.gif', '/path/to/image2.png', 'some/image3.jpg');
16.  Sets any event handlers that match a selector 

[code]$('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"); });

17. Find the selected option element

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

Hide elements that contain specific values

$("p.value:contains('thetextvalue')").hide();

Automatically scroll to specific areas of the 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();

20. Detect various browsers

Detect Safari (if( $.browser.safari)), Detect IE6 and over (if ($.browser.msie && $.browser.version > 6 )), Detect IE6 and below (if ($.browser.msie && $.browser.version <= 6 )), Detect FireFox 2 and above (if ($.browser.mozilla && $.browser.version >= '1.8' ))

Replace the words in the string

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

22. Close the right-click menu

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

23. 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();

24. Determine if an element exists

if ($('#someDiv').length) {

//hooray!!! it exists...

}

25. Use jQuery to judge left and right mouse clicks

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

Displays or deletes the default values for the input fields

//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[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]); } }); }); <INPUT value="Enter Username here.." type=text>

28. Dynamically create elements into the DOM

var newgbin1Div = $('');

newgbin1Div.attr('id','gbin1.com').appendTo('body');

29. Limit the number of characters in a textarea

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: 

$('#gbin1textarea').maxLength(500);

30. Create a basic test case for the function

//Separate tests into modules.

module("Module B");

test("some other gbin1.com 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" ); 

});