Fresh JQuery Programmer Interview Preparation Guide

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The plugin can be considered to be simply a new method that can be used by a user to extend the prototype object of a jquery. A plugin performs some actions on a collection of elements. Each method that comes with the jquery core can be considered to be a plugin.

The code for creating a plugin that would add and remove a class on hover would be as follows:
(function($)
{
$.fn.hoverClass = function(c)
{
return this.hover(
function() { $(this).toggleClass(c); }
);
};
})(jQuery);

// using the plugin
$('li').hoverClass('hover');

The two most common methods of sending a request to a server are :

1. GET method : The get method is mostly used for non destructive operations. These operations get data from the server and does not change the data on it. A good example of the application of the search query to a server. In most of the cases GET will send all of the data to be sent in the form of a query string.
2. POST method : The POST method is primarily used for destructive operations. These operations can change the data on a server. A good example is a user saving an entry on a site will get the POST request. These requests are not cached by the browser. A query can be a part of a url but any data that is to be sent is done separately as post data.

The height( ) method gets the current computed, pixel, height of the first matched element.

The remove( expr ) method removes all matched elements from the DOM.

1. jQuery Selectors are used to select one or a group of HTML elements from your web page.
2. jQuery support all the CSS selectors as well as many additional custom selectors.
3. jQuery selectors always start with dollar sign and parentheses: $().
4. There are three building blocks to select the elements in a web document.

1) Select elements by tag name
Example : $(div)
It will select all the div elements in the document.

2) Select elements by ID
Example : $("#xyzid")
It will select single element that has an ID of xyzid.

3) Select elements by class
Example : $(".xyzclass")
It will select all the elements having class xyzclass.

The css( name, value ) method sets a single style property to a value on all matched elements.

The starting point of jQuery code execution is $(document).ready() function which is executed when DOM is loaded.

The css( name ) method returns a style property on the first matched element.

jQuery library comes in 2 different versions Development and Production/Deployment. The deployment version is also known as minified version. So .min.js is basically the minified version of jQuery library file. Both the files are same as far as functionality is concerned. but .min.js is quite small in size so it loads quickly and saves bandwidth

The parent( [selector] ) method gets the direct parent of an element. If called on a set of elements, parent returns a set of their unique direct parent elements.

class selectors are the slow compare to ID and element.

The andSelf( ) method adds the previous selection to the current selection.

Using $.type(Object) which returns the built-in JavaScript type for the object.

The html( val ) method sets the html contents of every matched element.

$('.selected'). This selector is known as class selector. We need to prefix the class name with "." (dot).

The preventDefault() method of Event object prevents the browser from executing the default action.

Deferred and promise are part of jQuery since version 1.5 and they help in handling asynchronous functions like Ajax.

No. jQuery is not a replacement of JavaScript. jQuery is a different library which is written on top of JavaScript. jQuery is a lightweight JavaScript library that emphasizes interaction between JavaScript and HTML.

The .finish() method stops all queued animations and places the element(s) in their final state. This method was introduced in jQuery 1.9.

eq() returns the element as a jQuery object. This method constructs a new jQuery object from one element within that set and returns it. That means that you can use jQuery functions on it.

get() return a DOM element. The method retrieve the DOM elements matched by the jQuery object. But as it is a DOM element and it is not a jQuery-wrapped object. So jQuery functions can't be used.

ID and element selectors are the fastest selectors in jQuery.

The stopImmediatePropagation() method of Event object stops the rest of the handlers from being executed.

Client side scripting.

e.preventDefault() will prevent the default event from occurring, e.stopPropagation() will prevent the event from bubbling up and return false will do both.

A plug-in is piece of code written in a standard JavaScript file. These files provide useful jQuery methods which can be used along with jQuery library methods. jQuery plugins are quite useful as its piece of code which is already written by someone and re-usable, which saves your development time.