30 classic jQuery code development tips
- 2020-03-30 04:36:45
- OfStack
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" );
});