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Friday, 3 April 2015

Ajax Interview Questions and Answer for 1 Year Experienced




Ajax Interview Questions and Answer for Experienced

Question: How to Abort ajax requests using jQuery?
Use abort() function to abort a ajax request.
See Example Below:
var ajaxRequest = $.ajax({
    type: "POST",
    url: "/ajax",
    data: "name1=value1&name2=value2",
    success: function(msg){
       //here success comes
    }
});

//Abort the ajax request
ajaxRequest.abort()

When you abort the ajax call, you can see ajax request as aborted in browser console.


Question: How to redirect a page after success of Ajax call?
You can use window.location.href, to redirect.
See Example Below:
$.ajax({
    type: "POST",
    url: "/ajax",
    data: "name1=value1&name2=value2",
    success: function(msg){
        if(msg.success){
            window.location.href='/newpage.php';
        }
       //here success comes
    }
});



Question: How do I test an empty object?
You can use jQuery isEmptyObject().
See Example Below:
var myArray=new Array();
console.log($.isEmptyObject(myArray));//return true

var myArray=new Array('This is message');
console.log($.isEmptyObject(myArray));//return false


Question: How to submit a form in Ajax?
We can use jQuery ajax function to submit a Form.
See Example Below:
Following is Javascript function
   function onSubmitFunction(){
    $.ajax({
        type: "POST",
        url: "/ajax",
        data: $('#mytestForm').serialize(),
        success: function(msg){
            if(msg.success){
               //here success comes
            }

        }
    });
    return false;
}

Following is HTML Code
<form id="mytestForm" onsubmit="return onSubmitFunction()">
Name: <input name="name" type="text" /><input name="submit" type="submit" value="Submit" />
</form>



Question: How to get the value of textarea?
You can use val function of jQuery to get the text of textarea.
See Below:
console.log($('textarea#idOfTextArea').val());


Question: How to send AJAX call without jQuery?
For sending ajax call in IE7+, Firefox, Chrome, Opera, Safari
XMLHttpRequest
For sending ajax call in IE
use ActiveXObject

See Example Below:
function callAjax(url,method) {
    var xmlhttp;
    if (window.XMLHttpRequest) {
            // code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp = new XMLHttpRequest();
    } else {
            // code for IE6, IE5
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }

    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == 4) {
            if (xmlhttp.status == 200) {

                //console.log(xmlhttp.responseText);
            }
        }
    }

    xmlhttp.open(method, url, true);
    xmlhttp.send();
}
callAjax('/ajax?data=1','GET')


Question: How to make all ajax call cache Free?
$.ajaxSetup ({
    // Disable the caching of AJAX responses for all Ajax
    cache: false
});


Question: How to download file?
very simple
window.location="/folder/file.pdf"


Question: How can I add a custom HTTP header in Ajax?
Just Use the header parameter to set the custom header
$.ajax({
    url: '/ajax',
    headers: { 'x-my-custom-header': 'I am good' }
});



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