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Wednesday, 16 September 2015

jQuery Ajax Interview Questions and Answers for Experienced

jQuery Ajax Interview Questions and Answers for Experienced


Question: What is the difference between jQuery.get() and jQuery.ajax()?
$.get( "/ajax/add-user", { name: "Arun", company: "web-technology-experts-notes.in", gender:"Male" } );
$.get executes an Ajax request with using of GET Method.

$.ajax({
    type: "POST",
    url: "/ajax",
    data: "name=Arun&company=web-technology-experts-notes.in&gender=male",
    success: function(msg){
       console.log(msg); 
       
    }
});

$.ajax you full control over the Ajax request. In this you can use any method like GET or POST. I think you should use this only, if the other methods did not fulfill your requirement.
You can do lot of customization in this like caching and Ajax method etc


Question: What is the use of jQuery load method?
It is AJAX method which is used to load the data from a server and assign the data into the element without loading the page.


Question:What are the security issues with AJAX?
  1. Source code written in ajax easily visiable.
  2. Attrackers can send the the data to same API Call
  3. Attrackers can view the Request/Response in Ajax call.
  4. Attacker can view the full response and can hit and trial.



Question: How many types of ready states in ajax?
0: Request not initialized
1: Server connection established
2: Request received
3: Processing request
4: Request finished and response is ready


Question: List Some Popular Ajax Frameworks?.
  1. jQuery.
  2. script.aculo.us
  3. Prototype
  4. MooTools
  5. ExtJS
  6. Qooxdoo
  7. Yahoo! UI Library (YUI)
  8. MochiKit
  9. Midori
  10. The Dojo Toolkit



Question: What exactly is the W3C DOM?
The W3C Document Object Model (DOM) is defined by the W3C.
The DOM is a platform and language-neutral interface that allows programs and scripts to dynamically access/update the content of a document.


Question: What is the XMLHttpRequest object in AJAX?
It is way to update the web content from server without reloading the page.


Question: How can we abort the current XMLHttpRequest in AJAX?
use abort() function. For Example:
var xhr;    
xhr = $.ajax({
    url: 'ajax/get-user-details/user_id/3',
    success: function(data) {
        console.log(data);
    }
})
    
fn();

//Abort the Ajax call
if(xhr && xhr.readystate != 4){
  xhr.abort();  
}



Question: How to cancel all the active ajax call?
Every time you create an ajax request you should use a variable to store it, you can use array object to store multiple ajax.
Now you can use abort() function to abort each ajax call.


Question: How to debug Ajax call
You can use debug tools of browser.
like firebug in Mozilla.
Inspect element in Google Chrome

Question: How to convert an object to a string?
var javascriptObject = {name: "Web", "URL": "http://www.web-technology-experts-notes.in/"};
JSON.stringify(javascriptObject, null, 2);



Question: How to convert an string to a object?
var javascriptObject = '{name: "Web", "URL": "http://www.web-technology-experts-notes.in/"}';
JSON.parse(javascriptObject, null, 2);



Question: How can I add a custom HTTP header to ajax request with js or jQuery?
$.ajax({
    url: '/ajax/get-user-details/user_id/3',
    headers: { 'x-my-custom-header': 'some value' },
    success: function(data) {
        console.log(data);
    }
});



Question: How to determine if ajax timeout error comes?
$.ajax({
     url: '/ajax/get-user-details/user_id/3',
    type: "GET",
    dataType: "json",
    timeout: 1000,
    success: function(data) { 
        console.log(data);
     },
    error: function(x, t, m) {
        if(t==="timeout") {
            console.log("got timeout");
        } else {
            console.log(t);
        }
    }
});?


Question:How to send an https ajax call on http page?
Add the Access-Control-Allow-Origin header from the server
Access-Control-Allow-Origin: https://www.myexample.com




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