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jquery interview questions

Top jquery frequently asked interview questions

$(document).ready equivalent without jQuery

I have a script that uses $(document).ready, but doesn't use anything else from jQuery. I'd like to lighten it up by removing the jQuery dependency.

How can I implement my own $(document).ready functionality without using jQuery? I know that using window.onload will not be the same, as window.onload fires after all images, frames etc have been loaded.


Source: (StackOverflow)

Is Safari on iOS 6 caching $.ajax results?

Since the upgrade to iOS 6, we are seeing Safari's web view take the liberty of caching $.ajax calls. This is in the context of a PhoneGap application so it is using the Safari WebView. Our $.ajax calls are POST methods and we have cache set to false {cache:false}, but still this is happening. We tried manually adding a TimeStamp to the headers but it did not help.

We did more research and found that Safari is only returning cached results for web services that have a function signature that is static and does not change from call to call. For instance, imagine a function called something like:

getNewRecordID(intRecordType)

This function receives the same input parameters over and over again, but the data it returns should be different every time.

Must be in Apple's haste to make iOS 6 zip along impressively they got too happy with the cache settings. Has anyone else seen this behavior on iOS 6? If so, what exactly is causing it?


The workaround that we found was to modify the function signature to be something like this:

getNewRecordID(intRecordType, strTimestamp)

and then always pass in a TimeStamp parameter as well, and just discard that value on the server side. This works around the issue. I hope this helps some other poor soul who spends 15 hours on this issue like I did!


Source: (StackOverflow)

jQuery's jquery-1.10.2.min.map is triggering a 404 (Not Found)

I'm seeing error messages about a file, min.map, being not found:

GET jQuery's jquery-1.10.2.min.map is triggering a 404 (Not Found)


Screenshot

enter image description here

Where is this coming from?


Source: (StackOverflow)

Creating a div element in jQuery

How do I create a div element in jQuery?


Source: (StackOverflow)

How to move an element into another element?

I would like to move one DIV element inside another. For example, I want to move this (including all children):

<div id="source">
...
</div>

into this:

<div id="destination">
...
</div>

so that I have this:

<div id="destination">
  <div id="source">
    ...
  </div>
</div>

Source: (StackOverflow)

How do I insert an Item into an array at a specific Index?

I am looking for a Javascript array insert method, in the style of:

arr.insert(index, item)

Preferably in jQuery, but any Javascript implementation will do at this point.


Source: (StackOverflow)

Convert form data to JavaScript object with jQuery

How do I convert all elements of my form to a JavaScript object?

I'd like to have some way of automatically building a JavaScript object from my form, without having to loop over each element. I do not want a string, as returned by $('#formid').serialize();, nor do I want the map returned by $('#formid').serializeArray();


Source: (StackOverflow)

Get current URL in JavaScript?

I am using jQuery. How do I get the path of the current URL and assign it to a variable?

Example URL:

http://localhost/menuname.de?foo=bar&amp;number=0

Source: (StackOverflow)

jQuery scroll to element

I have this input element:

<input type="text" class="textfield" value="" id="subject" name="subject">

Then I have some other elements, like other text inputs, textareas, etc.

When the user clicks on that input with #subject, the page should scroll to the last element of the page with a nice animation. It should be a scroll to bottom and not to top.

The last item of the page is a submit button with #submit:

<input type="submit" class="submit" id="submit" name="submit" value="Ok, Done.">

The animation should not be too fast and should be fluid.

I am running the latest jQuery version. I prefer to not install any plugin but to use the default jQuery features to achieve this.


Source: (StackOverflow)

Abort Ajax requests using jQuery

Using jQuery, how can I cancel/abort an Ajax request that I have not yet received the response from?


Source: (StackOverflow)

How to detect a click outside an element?

I have some HTML menus, which I show completely when a user clicks on the head of these menus. I would like to hide these elements when the user clicks outside the menus' area.

Is something like this possible with jQuery?

$("#menuscontainer").clickOutsideThisElement(function() {
    // hide the menus
});

Source: (StackOverflow)

Format a Microsoft JSON date?

I'm taking my first crack at Ajax with jQuery. I'm getting my data onto my page, but I'm having some trouble with the JSON data that is returned for Date data types. Basically, I'm getting a string back that looks like this:

/Date(1224043200000)/

From someone totally new to JSON - How do I format this to a short date format? Should this be handled somewhere in the jQuery code? I've tried the jQuery.UI.datepicker plugin using $.datepicker.formatDate() without any success.

FYI: Here's the solution I came up with using a combination of the answers here:

function getMismatch(id) {
  $.getJSON("Main.aspx?Callback=GetMismatch", 
    { MismatchId: id },

    function (result) {
      $("#AuthMerchId").text(result.AuthorizationMerchantId);
      $("#SttlMerchId").text(result.SettlementMerchantId);
      $("#CreateDate").text(formatJSONDate(Date(result.AppendDts)));
      $("#ExpireDate").text(formatJSONDate(Date(result.ExpiresDts)));
      $("#LastUpdate").text(formatJSONDate(Date(result.LastUpdateDts)));
      $("#LastUpdatedBy").text(result.LastUpdateNt);
      $("#ProcessIn").text(result.ProcessIn);
    }
  );

  return false;
}

function formatJSONDate(jsonDate) {
  var newDate = dateFormat(jsonDate, "mm/dd/yyyy");
  return newDate;
}

This solution got my object from the callback method and displayed the dates on the page properly using the date format library.


Source: (StackOverflow)

.prop() vs .attr()

So jQuery 1.6 has the new function prop().

$(selector).click(function(){
    //instead of:
    this.getAttribute('style');
    //do i use:
    $(this).prop('style');
    //or:
    $(this).attr('style');
})

or in this case do they do the same thing?

And if I do have to switch to using prop(), all the old attr() calls will break if i switch to 1.6?

UPDATE

See this fiddle: http://jsfiddle.net/maniator/JpUF2/

The console logs the getAttribute as a string, and the attr as a string, but the prop as a CSSStyleDeclaration, Why? And how does that affect my coding in the future?


Source: (StackOverflow)

How do I return the response from an asynchronous call?

I have a function foo which makes an Ajax request. How can I return the response from foo?

I tried to return the value from the success callback as well as assigning the response to a local variable inside the function and return that one, but none of those ways actually return the response.

function foo() {
    var result;

    $.ajax({
        url: '...',
        success: function(response) {
            result = response;
            // return response; // <- I tried that one as well
        }
    });

    return result;
}

var result = foo(); // It always ends up being `undefined`.

Source: (StackOverflow)

jQuery document.createElement equivalent?

I'm refactoring some old JavaScript code and there's a lot of DOM manipulation going on.

var d = document;
var odv = d.createElement("div");
odv.style.display = "none";
this.OuterDiv = odv;

var t = d.createElement("table");
t.cellSpacing = 0;
t.className = "text";
odv.appendChild(t);

I would like to know if there is a better way to do this using jQuery. I've been experimenting with:

var odv = $.create("div");
$.append(odv);
// And many more

But I'm not sure if this is any better.


Source: (StackOverflow)