This post explains how you can send the HTML5 FormData
object as an AJAX request with jQuery. If you’re simply looking to learn how you can submit a form via AJAX using jQuery please checkout my other blog post instead; Submitting a form as an AJAX request using jQuery.
HTML5 introduces FormData
to allow developers to build forms objects dynamically (and can even include files from the user’s file system), and then to send this form object via AJAX. You can easily use FormData
with an XMLHttpRequest
by passing the FormData
instance as the parameter to xhr.send()
. However, what if you want to send the FormData
using jQuery?
Unfortunately, it’s not as easy as setting the data
attribute to the FormData
instance; jQuery runs anything that isn’t a string through jQuery.param()
to serialize the objects keys into key1=a&key2=b
etc; running FormData
through this doesn’t end too nicely.
However one of jQuery.ajax()
‘s many options is processData
, which allows you to turn off this behaviour by setting it’s value to false
. So, to use FormData
with jQuery.ajax()
it’s as simple as:
var formData = new FormData($('form')[0]); // Create an arbitrary FormData instance
jQuery.ajax('/endpoint.php', {
processData: false,
contentType: false,
data: formData
});
Note we’ve also had to set contentType
to false as well; unless contentType
is specified as an option to jQuery.ajax()
, jQuery reverts to the default of "application/x-www-form-urlencoded"
. By setting contentType
to false we prevent this option from being set, and the browser implementation of XMLHttpRequest
(which jQuery uses behind the scenes of course) will set the correct Content-Type
header for us.
Be aware that no amounts of jQuery will make FormData
cross browser. Whilst most browsers have supported FormData
since the stone age (Chrome 7, Firefox 4.0 and Safari 5), Internet Explorer and Opera are the noticeable exceptions, with support only being added in Internet Explorer 10 and Opera 12 respectively. As there’s no real polyfill/ fallback you can employ for FormData
, you should use feature detection and degrade gracefully as appropriate.
if (!("FormData" in window)) {
// FormData is not supported; degrade gracefully/ alert the user as appropiate
}
@ravisankar: If you create a
FormData
instance from aform
, all fields will be included.For example, given a form with id “the-form”, which has a file, checkbox, text field etc., calling
var fd = new FormData(document.getElementById('the-form'));
will give you aFormData
instance which contains all fields.For me its showing empty array on PHP. After sending fromdata i print that on php. Its showing the empty data
I am getting the error:
TypeError: Argument 1 of FormData.constructor does not implement interface HTMLFormElement.
Can you explain what it means?
Hi,
I’m getting the same problem: TypeError: Argument 1 of FormData.constructor does not implement interface HTMLFormElement.
The line
var fd = new FormData(document.getElementById('the-form'));
causes the problem. So I replace the line with thisvar fd = new FormData(document.getElementById('the-form')[0]);
… since the first one returns the an array of DOM Object and we required only the form object. Solved !! Thanks !! 😀
What if i write
It’s not taking the action:”test” So the record is not inserted in db. Based on this action:”test”, I made a function in maincontroller that will encode and decode all form data in json format and then transfer it to model for insertion in db.
Could you please tell me what’s the problem in this code??
@wasim: It means you’re passing something other than a form element to `FormData`. Make sure you’re not passing a jQuery object which wraps a form element; it must be the raw element; that’s what the [0] in my code snippet ensures.
@Tathagata:
document.getElementById
returns only one element.document.getElementsByTagName
returns an array of elements, so perhaps you were using that instead; but either way, usingdocument.getElementById()[0]
wouldn’t solve the problem.@AB: FormData simply doesn’t work like that. If you want to change the action of the form, use
this.action = "test"
(assuming #js-ajax-php-json is your form element). If you want to AJAX submit your form data to “test”, simply alter your$.ajax
call (e.g. change"/endpoint.php"
in my code sample to"test"
)What does 0 refer to?
var formData = new FormData($('form')[0]);
Thank you.
Hi ananth,
$('form')
returns a jQuery object, but we need to pass a HTML element toFormData
. `[0]` does that for us. It is the same as calling$('form').get(0)
.Hope that clears it up!
var formData = new FormData($(‘form’)[0]);
This works fine in chrome but when i check in Firefox it showing undefine.
Any idea?
Hi sanjeev. I would check your HTML and ensure that it is valid (e.g. by running it through http://validator.w3.org). I have just tested
var formData = new FormData($('form')[0])
on Firefox 45.0.1, and it works fine for me (http://jsfiddle.net/ea04htLu/). If you continue to have problems, feel free to post a MCVE (including your HTML) to Stack Overflow, and ping me a link!Regards,
Matt