Tuesday, 8 January 2019

Jquery

  1. Answer :
    Jquery is javascript library and it is used for HTML DOM access (manipulating and traversing of HTML DOM elements). It provides most powerful feature of event handling as well.
  2. Answer :
    Jquery can be used along with other libraries. It works with simple and complex javascript and AJAX.
  3. Answer :
    We can use Jquery by downloading the jquery and use it in our project or can use CDNs available from Google, Microsoft and give the CDN URL in ASPX page.
  4. Answer :
    query is a library and Javascript is a language and Jquery provides full-fledged support for javascript language.
  5. Answer :
    ‘$’ is used as an alias for jquery.
    Below are the examples of how we can use it:
    Eg: $(‘#MyControl’)
  6. Answer :
    • “body.onload” method will be used only once in a page where as “document.ready” method can be used multiple times in a same page. “body.onload” method will be called once all the resources of the page are loaded. (images, css and DOM).
    • But “document.ready” method called once DOM is ready and it does not wait till other resources are loaded.
  7. Answer :
    Below are the main reasons where we can use Jquery:
    • To apply the css for the controls.
    • To give special effects for the controls.
    • Event Handling.
    • To provide the AJAX support.
  8. Answer :
    Access the control using ‘$’ and use the methods “Hide()” and “Show()” like below.
    For example:
    $(‘#MyControl’).Hide()
    $(‘#MyControl’).Show()
  9. Answer :
    Jquery is one of the most powerful libraries what we have and it provides event handling. This scenario can be handled by “OnClick” of the button. Below is the code snippet –
    <input type=”button” id=”myButton” onclick=”alert(‘Hi’)” />
  10. Answer :
    In javascript we have several methods to find the controls like – “getElementByName” and “getElementByID”, which is used to find the control based on Name of the control and ID of the control respectively. Similarly in Jquery we have find the controls using selectors. Below are some of the selectors -
    • “*” - To Find all the elements of the page.
    • “#” – Used to find the control by ID.
    • “.” - Used to find the control by Class.
  11. Answer :
    No. If the Jquery file added in master page then content pages will going to use that.
  12. Answer :
    Advantage of using minified verison of Jquery will mainly be performance. Size of the minified jquery file will be around 76KB where as the normal Jquery file size will be around 180KB.
  13. Answer :
    Below is the sample code snippet:
    $(‘.MyControl’).Hide()
  14. Answer :
    Both are used to find number of elements in an object. “Length” will be used commonly because it’s faster compared to “size” because “length” is a property and “size” is a method.
  15. Answer :
    Below is the code snippet used to set the page title:
    $(function(){
    $(document).attr(“title”, “A4 Academics”);
    });
  16. Answer :
    Connect method is used to bind one function to another and it’s used to execute the function when a function is executed from another object.
  17. Answer :
    Jquery supports AJAX calls, below is the code snippet of AJAX in Jquery –
    $.ajax({
    url: ‘MyURL',
    success: function(response) {
    //My Code goes here
    },
    error: function(err) {
    //My Code goes here }
    });
  18. Answer :
    Jquery.Conflict method is used in case other client side libraries used along with Jquery then we will use this method.
    Eg: Prototype.js can be used with Jquery and this Prototype.js also uses “$” symbol for accessing the element. So for this purpose we are using Jquery.Conflict method.
  19. Answer :
    CDN is known as – “Content Distribution Network”, which is a network of servers which is deployed in large data center and can be accessed using internet.
  20. Answer :
    Below are the advantages of using CDNs:
    • Performance will be improved as there would not be much load on server.
    • Jquery libraries will be loaded faster.
    • Caching for the Jquery libraries will be enabled on use of CDNs.
  21. Answer :
    Following are the list of providers gives CDNs for Jquery library:
    • Microsoft
    • Google
    • Jquery
  22. Answer :
    “this” refers to the current element in the scope. “this” will be used in traditional javascript and “$(“this”)” if used then we will get the benefits of Jquery methods.
    For example:
    Using “$(this)” -
    $(document).ready(function(){
    $('#mycontrolid').change(function(){
    alert($(this).text());
    });
    });
    Using “this” -
    $(document).ready(function(){
    $('# mycontrolid'').change(function(){
    alert(this.innerText);
    });
    });
  23. Answer :
    $(document).ready(function(){
    if ($('#mycontrolid’).is(':empty')){
    //Code here for Empty element
    }
    });
  24. Answer :
    $(document).ready(function(){
    if ($('# mycontrolid’).length > 0){
    //Code Here if element exists.
    });
    });
  25. Answer :
    For iterating over objects we will be using this method. Each function uses “length” property of the object internally. Index and Text of each object can be fetched during iteration.
  26. Answer :
    In DOM structure “parents” method is used to traverse all along the DOM tree, whereas “parent” method is used to traverse only one level.
  27. Answer :
    Empty method is generally used to remove the child elements and the text associated to the elements.
    For example:
    Hi, A4 Academics. 
    In the above scenario nothing will be shown in UI as all the child controls and text will be removed.
  28. Answer :
    Below is the code snippet to check/uncheck radio buttons:
    // Check #mycontrolid
    $('#mycontrolid').attr('checked', true);
    // Uncheck #mycontrolid
    $('#mycontrolid').attr('checked', false);
  29. Answer :
    • “bind” and “live” methods are used to attach the events for the controls but there are pros and cons for each. 
    • “bind” – This method is used to attach the events for the elements which are static. We can not attach the events for the dynamic elements.
    • “live” – “live” method supports dynamic element event handling. But it has performance issues if you used all along the page.
  30. Answer :
    “clone” method is used to copy the matched elements. So all its childrens are also being copied along with the parent element.
    For example:
    $(document).ready(function(){
    $('#mycontrolid').click(function(){
    $('#mySpan').clone().prependTo("div");;
    return false;
    });
    });
  31. Answer :
    This method is used to prevent the default action from happening.
    For example:
    $("#mycontrolid").click(function(event){
    event.preventDefault();
    });
  32. Answer :
    This method is used to stop the event bubbling from the child elements. It prevents parent being notified to the child events.
    Method – “event.isPropagationStopped()” can be used to check whether method – “stopPropagation” was called or not.
  33. Answer :
    It means select all the div elements with class – “parent”.
  34. Answer :
    Below are some of the methods used:
    • Toggle()
    • FadeIn()
    • FadeOut()
    • Hide()
    • Show()
  35. Answer :
    “Childrens” method is used to find the child controls of the element but its limited to only one level where as “find” method can be used to find the controls in any level in DOM tree.
  36. Answer :
    “data” method is used to attach the data to the elements in DOM. When the element is removed data also will be removed.
    For example:
    jQuery.data( document.body, "a4academics", 40 );
  37. Answer :
    In MVC we can use these Jquery Plugins in the form of rules like below -
    $('#MyControlId').rules("add", {
    required: true
    });
  38. Answer :
    “Animate” method is used for animation in Jquery. This method is used to change the element look and feel and give extra effects to the elements.
    For example:
    $("#MyControlID").animate({height:"45px"});
  39. Answer :
    In Jquery, we have to use the method called – “stop()” to stop the animation.
  40. Answer :
    We can use the property – “fx.off” to disable the Jquery animation. Set the property value to true then it will disable the animation in Jquery.
  41. Answer :
    “Clone” method is used to clone the set of controls, which basically means to copy the set of elements which are matched on selectors. It copies the descendant elements along with the parent element.
    For example:
    $(document).ready(function(){
    $('#mycontrolid').click(function(){
    $('#mycontrolid').clone().appendTo('body');
    return false;
    });
    });
  42. Answer :
    By Default “clone” method does not clone the events unless it is being instructed to copy. When “clone” method is being instructed to clone the events also then along with elements, events are also being copied. “Clone”method takes a Boolean parameter, pass true in clone method to copy the events like below -
    $('#mycontrolid').clone(true).appendTo('body');
  43. Answer :
    • Attr() – This method is used to get the value of attribute of first element.
    • Prop() – This method is used to get the value of first element property.
  44. Answer :
    Yes. We can include different versions of Jquery in same page.
  45. Answer :
    We can use method – “holdReady” for this purpose. Below is the sample code snippet –
    $.holdReady(true);
  46. Answer :
    This is one of the powerful or robust feature of Jquery. Chaining means connecting multiple events/ selectors/ functions. Advantage of this would be – code will be easy to manage and good performance. Chain starts from left.
  47. Answer :
    Below is the sample code snippet:
    Old Code:
    $(document).ready(function(){
    $('#MyControlID').addClass('test');
    $('#MyControlID').css('color', 'yellow');
    $('#MyControlID').fadeIn('fast');
    });
    New Code after chaining:
    $(document).ready(function(){
    $('#MyControlID').addClass('test')
    .css('color', 'yellow')
    .fadeIn('fast'); 
    });
  48. Answer :
    Caching is temporary memory to store the data, which increases the performance of the application. So in Jquery we can use the similar concept to store the data instead of repeating as shown below:
    Old Code:
    $('#MyControlID').addClass('test');
    $('#MyControlID').css('color', 'yellow');
    New Code for caching:
    var $mycontrol = $("#MyControlID").css("color", "red");
    //Do somre stuffs here
    $mycontrol.text("Error occurred!");
  49. Answer :
    By using the property – “Jquery.Browser” we can write the browser specific code.
  50. Answer :
    Yes. Jquery supports AJAX.
    Below are some of the methods of AJAX:
    • Get()
    • Post()
    • GetJSON()
    • Ajax()
  51. Answer :
    Below is the sample code to explain:
    var Mypropertiescollection = $("#MyControlID").css([ "height", "width", "backgroundColor" ]);
    In the above code snippet variable – “Mypropertiescollection” will have array like below –
    {
    height: "100px",
    width: "200px", 
    backgroundColor: "#FF01EF"
    }
  52. Answer :
    “finish” method is used to stop the animations of the elements and bring the elements to its final state.
  53. Answer :
    Below are the list of 4 parameters which are used in AJAX calls –
    • Type
    • Cache
    • Data
    • URL
  54. Answer :
    Yes. We can debug Jquery file by using “debugger” keyword. We can add the “debugger” keyword to the line of Jquery file where we have to debug.
  55. Answer :
    Below is the code snippet which is used to sort the string array –
    $(document).ready(function(){
    var a4acarray = [ “Apple”,”Orange”,”Banana”];
    sortedarray = a4acarray.sort();
    $(“#mycontrolID”).html(sortedarray.join(“”));
    });
  56. Answer :
    “Resize” method used with window object. This method will be fired when the size of the browser window changes. For example
    $( window ).resize(function() {
    $( "#myControlID" ).append( "<div>Test Content</div>" );
    });
    As per above snippet when browser window’s size changes, content will be appended to the control – “myControlID”.
  57. Answer :
    Below is the sample code to bind to dropdown (selected) –
    <select id="myControlID">
    <option value="1">AA</option>
    <option value="2">BB</option>
    <option value="3">CC</option>
    <option value="4">DD</option>
    </select>
    Get the selected value –
    $("#myControlID option:selected").text();
  58. Answer :
    $('#myControlID').attr('disabled', true);
    $('#myControlID').attr('disabled', false);
  59. Answer :
    $('#myControlID').attr('checked', true);
    $('#myControlID').attr('checked', false);
  60. Answer :
    When we need to get the list of sibling elements then “sibling” method is used on parent element. Selectors can be used to filter the siblings. For example
    <ul>
    <li> itemA </li>
    <li id=”mycontrolID”> itemB </li>
    <li class=”mycontrolclass”> itemC </li>
    <li class=”mycontrolclass”> itemD </li>
    </ul>
    $(‘li#mycontrolID’).siblings().css(‘color’,’yellow’);
  61. Answer :
    Both methods are used to change the widths of the elements.
    For example:
    $(‘#myControlID’).css(‘width’,’150px’);
    $(‘#myControlID’).width(150);
    Above is the code to change the width of the element to 150px. As you can see “css(width)” method takes the width in pixels whereas for “width” method no need to explicitly mention the width in pixels.
  62. Answer :
    This method is used to give the animation effects to the elements in Jquery. SlideToggle method uses following parameters:
    • Speed – This is an optional parameter and it specifies the speed of animation effect.
    • Easing - This is an optional parameter and this specifies the speed of animation effect at different interval of time.
    • Callback – This parameter is optional and it accepts the callback function which will be executed once the execution of “slideToggle” method is completed.
  63. Answer :
    “param” method is used for object or array in the manner of serialization. While making AJAX calls, param method can be used to serialize the querystrings.
  64. Answer :
    customerObj=new Object();
    customerObj.name="A4Academics";
    customerObj.Designation=”IT”;
    $("#myControlID").click(function(){
    $("span").text($.param(customerObj));
    });
    Now the span element will have value like - “name=A4Academics&Designation=IT”
  65. Answer :
    “unbind” method is used to remove the event handlers associated to the element. This method can be used with selectors to remove the event handlers of the selected elements.
  66. Answer :
    Jquery Dialog is used like a pop up and if Jquery used in MVC then we can render the cshtml contents in Jquery Dialog and its used like a confirm box (as javascript) too.
  67. Answer :
    Below is the sample code for showing how we can do it –
    $(".MyClass1.MyClass2").css('color','green');
  68. Answer :
    We can select all <span> elements using below code –
    $("span:contains('a4academics’')")
  69. Answer :
    If we want to get the 4th <li> from the list of elements in <ul> then we can write code as below –
    $("ul li:eq(3)") // Index will start from 0.
  70. Answer :
    Below is the sample code snippet for this scenario –
    $("tr:even").css('color','green')
    $("tr:odd").css('color','blue')
  71. Answer :
    Below is the code snippet for this scenario:
    • $("ul li:gt(5)").css('color','green')
    • $("ul li:lt(10)").css('color','blue')
  72. Answer :
    Below is the code snippet for this scenario:
    $("p :not(:first)")
  73. Answer :
    jQuery is nothing but a collection of well written javascript code.
    In other words Jquery is ready made concise and fast JavaScript Library to be used.
  74. Answer :
    Below are the advatages of using jQery over JavaScript:
    1. Jquery is well written optimised javascript code so it will be faster in execution unless we write same standard optimised javascript code.
    2. Jquery is concise java script code ,means minimal ammount of code is to be written for the same functionality than the javascript.
    3. Javascript related Development is fast using Jquery because most of the functionality is already written in the library and we just need to use that.
    4. Jquery has cross browser support ,so we save time for supporting all the browsers.
  75. Answer :
    To use jQuery in ASP.NET web application follow the below steps:
    1. Go to http://jquery.com/(The official jQuery WebSite)
    2. Download latest .js jQuery file from the website. 
    3. Put it the script(or other folder) in the root of your web application 
    4. Add the below tag on the page where you want to use Jquery script type="text/javascript" src="script/jQueryDownLoadedFileName.js" /script
  76. Answer :
    JQuery min .js file is actully a minified version of Actual JQuery .js. The min files have less size but same content so this improves the performance.so You should prefer to use min files.
  77. Answer :
    Advantage of using $(document).ready(function () in jQuery is that the code inside this function will excecute only when the full page has been loaded so that there will be no error like the DOM object on which the Jquery has to execute is not loaded.
  78. Answer :
    Yes we can write more than one jquery $(document).ready(function ()
    in one page.This is helpful when you have large Jquery code and you want to split it in multiple files.
  79. Answer :
    To select an element with Id write as below:
    var divValue = $(''#sampleDivId'').val();
  80. Answer :
    To select an element with class write as below:
    $(".sampleClass").css("border","2px solid blue");
  81. Answer :
    • The difference between find() and children() methods
    • are that the children only travels a single level down the DOM tree
    • while the find travels at all level down the DOM tree.
  82. Answer :
    To test if an element exists we can use length method in jQuery as below:
    if $(''#mySampleDiv'').length )//Tests wheter the div with id mySampleDiv exists or not
    $(mySampleDiv).find(''div'');
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