Solved MCQ on JavaScript Window Object set-4

1. State whether the following statement are True or False for timers.

i) Like setTimeout(), setInterval() returns a value that can be passed to clearInterval() to cancel any future invocations of the scheduled function.

ii) If you call setTimeout() with a time of 0ms, the function you specify is not invoked right way.

A. i-True, ii-False

B. i-False,ii-True

C. i-True, ii-True

D. i-False, ii-False


2. The href property of the .......... object is a string that contains the complete text of the URL.

A. location

B. pathname

C. port

D. search


3. The .......... method of the Location object makes the window load and display the document at the URL you specify.

A. search()

B. load()

C. replace()

D. assign()


4) The ......... method removes the current document from the browsing history before loading a new document.

A. search()

B. remove()

C. replace()

D. assign()


5) Which of the following statements are True or False for Location object.

i) When a script unconditionally loads a new document, the replace() method is often a better choice than assign().

ii) In addition to the assign() and replace() methods, the Location object also defines reload(), which makes the browser reload the document.

iii) A only way to make the browser navigate to a new page is to simply assign the new full URL directly to the location property.

A. i-True, ii-True, iii-False

B. i-True, ii-False, iii-False

C. i-False, ii-True, iii-True

D. i-False, ii-False, iii-True


6) The .......... properties of the location object are writable, and setting them changes the location URL and also causes the browser to load a new document.

A. URL composition

B. URL decomposition

C. URL parsing

D. URL component


7) The properties like protocol, host, hostname, port, pathname, search and hash of Location object specify the various individual parts of the URL, they are known as ............ properties.

A. URL composition

B. URL decomposition

C. URL parsing

D. URL component


8) Which of the following statements are True for history property of the window object.

i) The length property of the history object specifies the number of elements in the browsing history list.

ii) The history object has back() and forward() methods that behave like the browsers back and forward buttons do.

A. i only

B. ii only

C. Both i and ii

D. None of the above


9) ......... method of the history object, takes an integer argument and can skip any number of pages forward for positive arguments or backward for negative arguments in the history list.

A. back()

B. backward()

C. forward()

D. go()


10) ........ method brings webpage back like clicking the back button twice.

A. history.go(-2)

B. history.back.back()

C. history.back(2)

D. history.go(2)


11) Match the following properties of Navigator object to their description.

i) appName            a) that identifies the operating system

ii) appVersion        b) all the information along with appVersion

iii) UserAgent        c) browser vender and version information

iv) platform           d) full name of the web browser

A. i-b, ii-c, iii-d, iv-a

B. i-c, ii-d, iii-a, iv-b

C. i-d, ii-c, iii-b, iv-a

D. i-a, ii-d, iii-c, iv-b


12) The .......... property specifies whether the browser is currently connected to the network.

A. navigator.online

B. geolocation

C. javaEnabled()

D. cookiesEnabled()


13) A ........... object that defines an API for determining the user's geographical location.

A. navigator.online

B. geolocation

C. javaEnabled()

D. cookiesEnabled()


14) .......... displays a model dialog box containing HTML formatted content and allows arguments to be passed to, and a value returned from, the dialog.

A.alert()

B. conform()

C. prompt()

D. showModelDialog()


15) State whether the following statements are True or False for methods for displaying simple dialog box on window object.

i) alert() displays a message to the user and waits for the user to dismiss the dialog.

ii) conform() displays a message, waits for the user to click an OK or Cancel button and returns positive or negative value.

iii) prompt() displays a message, waits for the user to enter a string, and returns that string.

A. i-True, ii-False, iii-True

B. i-True, ii-True, iii-False

C. i-False, ii-True, iii-True

D. i-False, ii-False, iii-False



Answers:

1) C. i-True, ii-True
2) A. location
3) D. assign()
4) C. replace()
5) A. i-True, ii-True, iii-False
6) B. URL decomposition
7) B. URL decomposition
8) C. Both i and ii
9) D. go()
10) A. history.go(-2)
11) C. i-d, ii-c, iii-b, iv-a
12) A. navigator.online
13) B. geolocation
14) D. showModelDialog()
15) A. i-True, ii-False, iii-True


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Solved MCQ on Basic Client Side JavaScript set-3


1. JavaScript can help to increase the user experience with which of the following method for a web page.

A. By creating animation and other effects to guide a user and help with page navigation.

B. By sorting the columns of a table to make it easier for searching on table.

C. By hiding certain content and revealing details progressively as the user "drills down" into that content.

D. All of the above.



2. Which of the following are the ways to embed Client side JavaScript code within HTML documents.

i) Inline, between a pair of <script> and </script> tags.

ii) From an external file specified by the src attribute of a <script> tag

iii) In an HTML event handler attribute, such as on-click or mouse over.

iv) In a URL that uses the special JavaScript protocol.

A. i, ii and iii only

B. ii, iii and iv only

C. i, ii and iv only

D. All i, ii, iii and iv



3. State Whether the following Statement about src attribute on JavaScript.

i) It simplifies the HTML files by allowing you to remove large blocks of JavaScript code from them.

ii) If a file of JavaScript code is shared by more than one page, it only needs to be downloaded once, by the first page that uses it.

iii) Linking to JavaScript code on Google servers can decrease the start-up time for the web pages, since the code already existed on all of the user's browser.

A. i-True, ii-False, iii-True

B. i-True, ii-True, iii-False

C. i-False, ii-True, iii-False

D. i-False, ii-False, iii-True



4) JavaScript code can register a/an ............. by assigning a function to a property of an element object that represents an HTML document in the document.

A. event handler

B. function handler

C. document handler

D. HTML handler



5) .......... specifies that the body of the URL is an arbitrary string of JavaScript code to be run by the JavaScript interpreter.

A. Javascript:web

B. JavaScript:code

C. JavaScript:protocol

D. JavaScript:interpreter




6) The ...... attribute causes the browser to defer execution of the script until after the document has been loaded and parsed and is ready to be manipulated.

A. sync

B. async

C. defer

D. All



7) The .......... attribute causes the browser to run the script as soon as possible but not to block document parsing while the script is being downloaded.

A. sync

B. async

C. defer

D. All



8) When the parser encounters a <script> element that has the ...... attribute set, it begins downloading the script text and continues parsing the document.

A. async

B. sync

C. parse

D. load



9) When the document is completely parsed, the document.readystate property changes to ......

A. ready

B. parsed

C. interactive

D. activated



10) Which of the following statements for restricted features of JavaScript is/are True.

A) A JavaScript program can open new browser windows, but must of the browsers restrict this feature.

B. A JavaScript program can close browser windows that it opened itself, but it is not allowed to close other windows without user conformation.

C. A script can read the content of documents loaded from different servers than the document that contains the script.

D. All of the above




11) ........... libraries are "frameworks" in the sense that they build a new higher-level API for client side programming on top of the standard and proprietary APIs offered by web browsers.

A. client-side framework

B. server-side framework

C. higher-level framework

D. web framework



12) The .......... library focuses on DOM and Ajax utilities, like jQuery does, and adds quite a few core-language utilities as well.

A. Dojo

B. Prototype

C. YUI

D. Closure



13) The ...... library is the client side library that Google uses for Gmail, Google Docs and other web applications.

A. Dojo

B. Prototype

C. GWT

D. Closure



14) ........ allow you to register a function to be invoked once or repeatedly after a specified amount of time has elapsed.

A. setTimeout()

B. setInterval()

C. Both A and B

D. None of the above



15) State True or False for the following Statements.

i) The setTimeout() method of the window object schedules a function to run after a specified number of milliseconds elapses.

ii) setTimeout() returns a value that can be passed to clearTimeout() to cancel the execution of the scheduled function.

iii) setTimeout() is like setInterval() except taht the specified function is invoked repeatedly at intervals of the specified number of milliseconds.

A. i-True, ii-False, iii-True

B. i-True, ii-True, iii-False

C. i-False, ii-True, iii-False

D. i-False, ii-False, iii-True




Answers:


1) D. All of the above.
2) D. All i, ii, iii and iv
3) B. i-True, ii-True, iii-False
4) A. event handler
5) C. JavaScript:protocol
6) C. defer
7) B. async
8) A. async
9) C. interactive
10) D. All of the above
11) A. client-side framework
12) B. Prototype
13) D. Closure
14) C. Both A and B
15) B. i-True, ii-True, iii-False


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Objective Questions on CSS Syntax and Property set-6


1) ....... media type is used for use with printed material and documents viewed onscreen in print preview mode.

A. Print

B. Projection

C. Aural

D. Screen



2) In CSS length measurement unit ....... defines a measurement in picas.

A. pi

B. pc

C. pt

D. px



3) In CSS length measurement unit ......defines a measurement in screen pixel.

A. pi

B. pc

C. pt

D. px




4) ........ defines a measurement relative to a font's x-height. The x-height is determined by the height of the font's lowercase letter x.

A. cm

B. em

C. ex

D. hx




5) Which of the following is the correct CSS code to set the background color of all h1, h2 and h3 elements to orange.

A. h1.h2.h3{background-color:orange;}

B. h1, h2, h3{background-color:orange;}

C. h1 h2 h3{background-color:orange;}

D. h1, h2, h3{set-background:orange;}




6) The CSS selector E>F selects ...

A. direct decedents

B. adjacent siblings

C. preceding siblings

D. all elements



7) The CSS selector E-F selects .....

A. direct decedents

B. adjacent siblings

C. preceding siblings

D. all elements



8) ........... selects all elements of E that have an attribute attr that starts with the value given in a list of hyphen-separated values.

A. E[attr-=value]

B. E[attr|=value]

C. E[attr~=value]

D. E[attr^=value]



9) .......... selects all elements of E that have the attribute attr that begins with the given value.

A. E[attr-=value]

B. E[attr|=value]

C. E[attr~=value]

D. E[attr^=value]



10) A single @charset rule can be used in a/an ........... to define character set encoding of the style rules and values.

A. external sheet

B. internal sheet

C. inline codes

D. Both A and B




11) An ......... rule can be used to define style rules for multiple media types in a single embedded style sheet.

A. @embedded

B. @media

C. @page

D. @multiple



12) An ........... rule is used to define a page block for printed styles. Generally, within this construct we see various CSS properties like size, page, and margin to control the dimensions of the page.

A. @embedded

B. @media

C. @page

D. @print



13) Which of the following are the sub properties of background property used in CSS Except.

A. background-color

B. background-scroll

C. background-image

D. background-repeat



14) Which of the following is the default value of background-image property in CSS.

A. url

B. inherit

C. none

D. both A and B



15) State whether the following statements are True or False.

i) Background-position property determines how a background image is positioned within the canvas space by associated element.

ii) The default value for background-attachment property is fixed.

iii) The background image requires a URL(complete or relative) to link it to the source image specified with the url() syntax.

A. i-True, ii-True, iii-False

B. i-True, ii-False, iii-False

C. i-False, ii-True, iii-True

D. i-True, ii-False, iii-True



16) Which of the following is/are the sub properties of border property in CSS.

A. border-width

B. border-style

C. border-color

D. All of the above



17) Match the following CSS cursor resizing property with their descriptions.

i) e-resize a) pointing north south.

ii) ne-resize b) pointing northwest-southeast

iii) nw-resize c) pointing northeast-southwest

iv) n-resize d) pointing east-west(left-right)

A. i-d, ii-c, iii-b, iv-a

B. i-c, ii-b, iii-a, iv-d

C. i-b, ii-c, iii-d, iv-a

D. i-d, ii-a, iii-b, iv-c



18) ......... property controls how spaces, tabs, and newline charters are handled in an element.

A. visibility

B. white-space

C. tab-space

D. line-space



19) ......... property controls the algorithm used to lay out the table, cells, rows, and columns.

A. table-layout

B. cell-layout

C. row-column-layout

D. None of the above



20) ......... property is used to force or prohibit a printing page break within an element.

A. page-break-outside

B. page-break-inside

C. printing-page-break

D. page-break-element


Answers:

1) A. Print
2) B. pc
3) D. px
4) C. ex
5) B. h1, h2, h3{background-color:orange;}
6) A. direct decedents
7) C. preceding siblings
8) B. E[attr|=value]
9) D. E[attr^=value]
10) A. external sheet
11) B. @media
12) C. @page
13) B. background-scroll
14) C. none
15) D. i-True, ii-False, iii-True
16) D. All of the above
17) A. i-d, ii-c, iii-b, iv-a
18) B. white-space
19) A. table-layout
20) B. page-break-inside
478f8ffac419307280ec7a8194f9ee837ed62daf3f47597227


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How to Create Show/Hide Effect in Image SlideShow Using JQuery

The fadeOut() effect presented on the post "How to create Fade Effect in Image Slideshow using JQuery" which I have already posted, makes elements invisible but retains space for them in the document layout.

The hide() method, by contrast, removes the elements from the layouts as if the CSS display property was set to none. When invoked with no arguments, hide() and show() simply hide or show the selected elements immediately. With a duration argument, however, they animate the hiding or showing process. hide() shrinks an element's width and height to 0 at the same time that it reduces the element's opacity to 0. show() reverses the process.

toggle() changes the visibility state of the elements, it is invoked on, if they are hidden, it calls show(), and it they are visible, it calls hide(). As with show() and hide(), you must pass a toggle() to get an animated effect. Passing true to toggle() is the same as calling show() with no arguments. Note also that if you pass two or more function arguments to toggle() it registers event handlers.

Here is an example that invokes methods for show/hide effect animation. The first image has show() effect animation, second image has hide() effect animation and the third animation has toggle() effect animation.

$("#img1").show(2000);
$("#img2").hide(3000);
$("#img3").toggle(1000);

Here are some examples to show show(), hide() and toggle() effects using jQuery.

Example of show() Effect 


<script>
  $(document).ready(function(){
    $(#btn1).click(function () {
      $("#img1").show(2000);
    });
  });
  </script>

<input type=button id="btn1" value="Start Show"/>
<img id="img1" src="img1.jpg">



Example of hide() Effect


<script>
  $(document).ready(function(){
    $(#btn2).click(function () {
      $("#img2").hide(3000);
    });
  });
  </script>

<input type=button id="btn2" value="Start Hide"/>
<img id="img2" src="img2.jpg">



Example of toggle() Effect 


<script>
  $(document).ready(function(){
    $(#btn3).click(function () {
      $("#img3").toggle(1000);
    });
  });
  </script>






<input type=button id="btn3" value="Start Toggle"/>
<img id="img3" src="img3.jpg">


Full jQuery code for Show/Hide effect image animation


<script 

src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
</script>

<style>
.show_hide
{
 box-shadow:1px 1px 5px 2px #6DC83C;
 position:relative;
 width:448px;
 height: 336px;
 border-radius:19px;
}

.show_hide img
{
 border-radius:19px;
 position:absolute;
 left:0;
 top:0;
}

</style>

<script>
$(function(){
 $('.show_hide img:gt(0)').hide();
 setInterval(function(){$('.show_hide :first-child').hide(3000).next('img').show(3000).end

().appendTo('.show_hide');}, 6000);
});
</script>

<div class="show_hide">
<img src="img1.JPG" />
 <img src="img2.JPG" />
 <img src="img3.JPG" />
</div>


Preview of Show/Hide effect image animation







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How to Create Animated Visual Effects Using jQuery

You can create animated visual effects by setting the CSS visibility property, i.e. making elements appearing and disappearing. Along with making an element appear and disappear, we might reduce the value of its opacity property over the certain period. This king of animated visual effect creates a more pleasing experience for user and jQuery makes them easy.

jQuery defines simple methods such as fadeIn() and fadeOut() for basic visual effects. You can also use an animate() method for producing more complex custom animations. 

Every animation has a duration that specifies how long the effect should last for. You can specify this as a number of milliseconds or by using a string. The string "fast" means 200ms and the sting "slow" means 600ms. If you specify a duration string that jQuery does not recognize, you will get a default duration of 400ms. 

$("#animation").fadeIn(); 
// It fades an element in over 400ms
$("#animation").fadeOut("fast"); 
// It fade outs over 200ms
$("#animation").fadeIn(5000);
//It fades an element in over 5000ms

You can also define new duration names by adding new string-to-number mappings to jQuery.fx.speeds as given below. 

jQuery.fx.speeds["medium-fast"]=3000;
jQuery.fx.speeds["medium-slow"]=5000;

Here is an example to create animated visual effects using methods fadeIn() and fadeOut() in jQuery 

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
<script>
jQuery.fx.speeds["medium-slow"]=3000;
jQuery.fx.speeds["very-slow"]=5000;
$(document).ready(function(){
 $("#btn1").click(function(){
$("#animation1").fadeIn(); 
$("#animation3").fadeIn(5000);
$("#animation5").fadeIn("medium-slow");
});
 $("#btn2").click(function(){
$("#animation2").fadeOut("fast");
$("#animation4").fadeOut("very-slow");
});
 });
</script>
<input type=button id="btn1" value="Start FadeIn"/><br/>
<div id="animation1" style="display:none;background:pink;">It fades an element in over 400ms</div><br/>
<div id="animation3" style="display:none;background:red">It fades an element in over 5000ms</div><br/>
<div id="animation5" style="display:none;background:yellow">It fades an element in over 3000ms</div><br/>

<input type=button id="btn2" value="Start FadeOut"/><br/>
<div id="animation2" style="background:red">It fade outs over 200ms</div><br/>
<div id="animation4" style="background:pink">It fade outs over 5000ms</div><br/>

Preview:







It fade outs over 200ms

It fade outs over 5000ms

You can also set the value of the document that was animated using a function as argument. Here is a jQuery code which quickly fade in an element and when it is visible, display some text in it. 

<script>
$(document).ready(function(){
$("#btn4").click(function(){
$("#message").fadeIn("fast", function() {$("#message").text("Hello this is animation");});
});});
</script>
<input type=button id="btn4" value="Start Animation"/><br/>
<div id="message" style="color:red"></div>

Preview:






Passing a callback function to an effect method allows you to perform actions at the end of an effect. However, that is is not necessary when you simply want to perform multiple effects in sequence. If you call an animation method on an element that is already being animated, the new animation does not begin right away but is deferred until the current animation ends. For example, you can make an element blink before fading in permanently. 

<script>
$(document).ready(function(){
$("#blinker").mouseover(function(){
$("#blinker").fadeIn(100).fadeOut(100).fadeIn(100).fadeOut(100).fadeIn();});
});
</script>
<div id="blinker" style="color:red"><h3>It blinks before fading in permanently</h3></div>

Preview:

It blinks before fading in permanently


jQuery's effect methods are declared to accept optional duration and callback arguments. It is also possible to invoke these methods with an object whose properties specify animation options. 

<script>
$(document).ready(function(){
 $("#btn3").click(function(){
$("#effect").fadeIn({
duration: "slow",
complete: function(){$(this).text("Animation was completed");}
});});});
</script>
<input type=button id="btn3" value="Start Animation"/>
<div id="effect" style="background:yellow">This is sample animation effect</div>

Preview:



This is sample animation effect


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How to Get and Set Element Attributes using jQuery

Some of the simplest and most common, operations on jQuery objects are those that get or set the value of HTML attributes, CSS styles, element content, or element geometry. In this post I am going to describe the methods to get or set HTML element attributes using jQuery.

How to Get and Set HTML Attributes using jQuery


You can get or set HTML attributes using attr() method in jQuery. The attr() method handles browser incompatibilities and special cases and allows you to use either HTML attributes names or their JavaScript property equivalents.

Here are some examples of uses of attr() method for getting or setting HTML attributes.

$("form").attr("action");  
// It gets the action attribute from the first form.

$("#icon").attr("src", "icon.gif");  
// It sets the src attributes for image with id icon.

$("a").attr("target", "_blank");  
// It set the target attributes for all links to load in new windows 

$("a").attr("target", function(){
 if(this.host==location.host) return "_self"
 else return "_blank";
});

This function sets the attribute of all external links load in new windows and internal links load in the same window.

There is another method related to attr() is removeAttr(), which is related function that completely removes an attributes from all selected elements.

Here an example of uses of removeAttr() method for removing HTML attributes.

$("a").removeAttr("target");

It removes the target attribute of link and makes all links load in the same window.

How to Get and Set CSS Attributes using jQuery


The css() method is very much like attr() method, but is works with the CSS styles of an element rather than the HTML attributes of the element.

When querying style values, css() returns the current style of the element and the returned value may come from the style attribute or from a style-sheet.

Here are some examples getting and setting CSS attributes using attr() method.

$("h1").css("font-weight"); 
// It gets font weight of first <h1>

$("h1").css("font-variant", "smallcaps"); 
// It sets font-variant property of <h1> to smallcaps.

$("h1").css({backgroundColor:"black",textColor:"white",
 fontVariant:"small-caps", padding: "10px 2px 4px 20px", 
 border:"dotted black 4px"});   
// It sets multiple styles at once for <h1>

How to Get and Set CSS Classes using jQuery


jQuery defines convenience methods for working with the class attribute. addClass() and removeClass() add and remove classes from the selected elements. toogleClass() adds classes to elements that don't already have them and removes classes from those that do. hasClass() tests for the presence of a specified class.

Here are are some examples for adding css classes, removing css classes, toggling css classes and testing css classes.

Adding CSS Classes

$("h1").addClass("hilite");  
// It adds a class to all <h1> elements

$("h1+p").addClass("hilite first"); 
// It adds two classes to elements after <h1>

$("section").addClass(function(n){return "scetion"+n;}); 
// It passes a function to add a custom class to each matched element

Removing CSS classes

$("p").removeClass("hilite");  
// It removes a class from all p elements

$("p").removeClass("hilite first"); 
// It removes two classes from <p> elements

$("section").removeClass(function(n){return "scetion"+n;}); 
// It passes a function to remove a custom class to each matched element

Toggling CSS Classes

$("tr:odd").toggleClass("oddrow"); 
// It adds the class if it is not there or remove if it is.

$("h1").toggleClass("big bold");   
// It toggles two classes at once. 

$("h1").toggleClass(function(n){
return "big bold h1-" +n; });  
// It toggles a computed class or classes.

$("h1").toggleClass("hilite", true); 
// It works like addclass

$("h1").toggleClass("hilite", false); 
// It works like removeclass

Testing CSS Classes

$("p").hasClass("first")  
// It tests any p element have class first

$("#lead").is("first") 
// It test any element with id lead have class first

The hasClass() method is less flexible than addclass(), removeClass, and toggleClass(). hasClass() works for only a single class name and does not support function arguments. It returns true if any of the selected elements has the specified CSS class and returns false if none of them do. The is() method is more flexible and can be used for the same purpose.

How to Get and Set HTML Form Values Using jQuery


For setting and querying the value attribute of HTML form elements val() method is used and it is also used for querying and setting the selection state of check-boxes, radio buttons, and select elements. Here are some examples of getting and setting HTML form values using val() method. 

$("#firstname").val()  
// It gets value from the firstname text field.

$("select #extras").val() 
// It gets array of values from <select multiple< from element. 

$("input:radio[name=ship]:checked").val() 
// It gets value of checked radio button.

How to Get and Set Element Content Using jQuery


The text() and html() methods query and set the plain-text or HTML content of an element or elements. When invoked with no arguments, text() returns the plain text content of all descendant text nodes of all matched elements. This works even in browsers that do not support the textContent or innerText properties. Here are some examples of getting and setting element content using text() and html() method 

var title=$("head title").text() //It gets document title
var headline=$("h1").html() 
//It gets the html of first <h1> element

$("h1").text(function(n,current){
 return "$" + (n+1) + ": "+current }); 
// It gives section number for each headings

How to Get and Set Element Geometry Using jQuery


To query or set the position of an element, use the offset() method. This method measures positions relative to the document and returns them in the form of an object with left and top properties that hold the X and Y coordinates. It you pass an object with these properties to the method, it sets the position you specify. Here are some examples of getting and setting element geometry using offset() method 

var elt=$("#sprite");
var position=elt.offset(); 
// It gets the current position of an elememt
position.top +=100;
// It changes its Y coordinate 100px.
elt.offset(position);

How to Get and Set Element Data Using jQuery


jQuery defines a getter or setter method named data() that sets or queries data associated with any document element or with the Document or window objects. You can also use removeData() method to remove data from an element or elements. Here are some examples of getting and setting element data using data() method removing data using removeData() method. 

$("div").data("x",1); 
//It sets some data "x" to div
$("div.nodata").removeData("x"); 
//It removes some data "x" from div with class nodata
var x=$("#mydiv").data("x"); 
//It query some data from element id "mydiv"


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How to Use jQuery With HTML?

jQuery() is a single global function defined by jQuery library. This function is so frequently used that the library also defines the global symbol $ as a shortcut for it.

This single global function with two names is the central query function for jQuery. For example, if you need to ask for the set of all <div> elements in a document, write the following code.

var divs=$("div");

The value returned by the jQuery() function represents a set of zero or more DOM elements is known as a jQuery object. jQuery objects define many methods for operating on the sets of elements they represent.

How to Obtain jQuery


jQuery library is free software. You can download if from http://www.jquery.com. Once you have download the code, you can include it in your web pages with a <script> element as given below.
<script src="jquery-1.11.2.min.js"></script>

Here the "min" in the filename indicates that this is the minimized version of the library, with unnecessary comments and whitespace removed, and internal identifiers replaced with shorter ones.

And another way to use jQuery in your web application is to allow a Content Distribution Network (CDN) to serve it using a URL like one of these. 

Google CDN


https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js
https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js

Microsoft CDN


http://ajax.aspnetcdn.com/ajax/jQuery/jquery-2.1.3.min.js
http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.11.2.min.js

jQuery CDN


http://code.jquery.com/jquery-2.1.3.min.js
http://code.jquery.com/jquery-1.11.2.min.js


If you use Google CDN, you can use "1.11" to get the latest release in the 1.11.x series, or just "1" to get the most current release less than 2.0.

The major advantage of loading jQuery from well-known URLs like these is that, because of jQuery's popularity, visitors to your website will likely already have a copy of the library in the browser's cache and no download will be necessary.

How to Use jQuery() Function


The jQuery() function is the most important one in the jQuery library. It is heavily overloaded, however, and there are four different ways you can invoke it.

The first, and the most common way to invoke $() is to pass a CSS selector to it. Which returns the set of elements from the current document that match the selector as given in the example below.

var id=$("#id");
var class=$(".class");

And the another way to invoke $() is to pass it an Element or Document or Window object. It simply wraps the element, document or window in a jQuery object and returns that object. Doing this allows you to use jQuery methods to manipulate the element rather than using raw DOM methods. For example you can call $(document) or $(this) to pass document or current element.

The third way to invoke $() is to pass it a string of HTML text. When you do this, jQuery creates the HTML element or elements described by that text and then returns a jQuery object representing those elements.

When invoked in this way, $() accepts an optional second argument. You can pass a document object to specify the document with which the elements are to be associated. If you do this, the object properties are assumed to specify the names and values of HTML attributes to be set on the object.

Here is an example, where three arguments are used to set the url, css of the image and the click event on the image. 

var img=$("<img />"),
    {src:url,
    css:{borderWidth:5},
    click:handleClick
    });

And the fourth way to invoke $() is to pass a function to it. If you do this, the function you pass will be invoked when the document has been loaded and the DOM is ready to be manipulated. For example here is a jQuery version of onLoad() function which is invoked when the document has loaded.

$(function(){
// jQuery code
});

Read Next:How to Get and Set Element Attributes using jQuery

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