FormData

The FormData interface provides a way to easily construct a set of key/value pairs representing form fields and their values, which can then be easily sent using the XMLHttpRequest.send() method. It uses the same format a form would use if the encoding type were set to "multipart/form-data".

You can also pass it directly to the URLSearchParams constructor if you want to generate query parameters in the way a <form> would do if it were using simple GET submission.

An object implementing FormData can directly be used in a for...of structure, instead of entries(): for (var p of myFormData) is equivalent to for (var p of myFormData.entries()).

Note: This feature is available in Web Workers.

Constructor

FormData()

Creates a new FormData object.

Methods

FormData.append()

Appends a new value onto an existing key inside a FormData object, or adds the key if it does not already exist.

FormData.delete()

Deletes a key/value pair from a FormData object.

FormData.entries()

Returns an iterator allowing to go through all key/value pairs contained in this object.

FormData.get()

Returns the first value associated with a given key from within a FormData object.

FormData.getAll()

Returns an array of all the values associated with a given key from within a FormData.

FormData.has()

Returns a boolean stating whether a FormData object contains a certain key.

FormData.keys()

Returns an iterator allowing to go through all keys of the key/value pairs contained in this object.

FormData.set()

Sets a new value for an existing key inside a FormData object, or adds the key/value if it does not already exist.

FormData.values()

Returns an iterator allowing to go through all values contained in this object.

Specifications

Specification
XMLHttpRequest Standard (XMLHttpRequest)
# interface-formdata

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
FormData
7
12
4
Before Firefox 7, specifying a Blob as the data to append to the object, the filename reported in the Content-Disposition HTTP header was an empty string, resulting in errors on some servers. Starting with Firefox 7, the filename blob is sent.
10
12
5
≤37
XHR in Android 4.0 sends empty content for FormData with blob.
18
4
Before Firefox 7, specifying a Blob as the data to append to the object, the filename reported in the Content-Disposition HTTP header was an empty string, resulting in errors on some servers. Starting with Firefox 7, the filename blob is sent.
12
5
1.0
FormData
7
12
4
10
12
5
≤37
18
4
12
5
1.0
append
7
12
4
Before Firefox 7, specifying a Blob as the data to append to the object, the filename reported in the Content-Disposition HTTP header was an empty string, resulting in errors on some servers. Starting with Firefox 7, the filename blob is sent.
10
With the "Include local directory pass when uploading files to a server" option enabled, IE will change the filename inside the Blob on the fly. To have direct control of the sent filename, the developer should send the filename as the third parameter value, i.e. formData.append(name, value, filename).
12
5
3
XHR in Android 4.0 sends empty content for FormData with blob.
18
4
Before Firefox 7, specifying a Blob as the data to append to the object, the filename reported in the Content-Disposition HTTP header was an empty string, resulting in errors on some servers. Starting with Firefox 7, the filename blob is sent.
12
5
1.0
delete
50
18
39
No
Yes
11.1
50
50
Yes
Yes
11.3
5.0
entries
50
18
44
No
37
11.1
50
50
44
37
11.3
5.0
forEach
50
18
47
No
37
11.1
50
50
47
37
11.3
5.0
get
50
18
39
No
37
11.1
50
50
39
37
11.3
5.0
getAll
50
18
39
No
37
11.1
50
50
39
37
11.3
5.0
has
50
18
39
No
Yes
11.1
50
50
Yes
Yes
11.3
5.0
keys
50
18
44
No
Yes
11.1
50
50
44
?
11.3
5.0
set
50
18
39
No
37
11.1
50
50
39
37
11.3
5.0
values
50
18
44
No
37
11.1
50
50
44
37
11.3
5.0
worker_support
50
79
39
No
37
13.1
50
50
39
37
13.4
5.0
@@iterator
50
18
44
No
37
11.1
50
50
44
37
11.3
5.0

See also

© 2005–2021 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/FormData