FormData.set()
The set()
method of the FormData
interface sets a new value for an existing key inside a FormData
object, or adds the key/value if it does not already exist.
The difference between set()
and FormData.append
is that if the specified key does already exist, set()
will overwrite all existing values with the new one, whereas FormData.append
will append the new value onto the end of the existing set of values.
Note: This method is available in Web Workers.
Syntax
There are two versions of this method: a two and a three parameter version:
formData.set(name, value); formData.set(name, value, filename);
Parameters
name
- The name of the field whose data is contained in
value
. value
- The field's value. In the two parameter version this is a
USVString
, or if it is not, it is converted to a string. In the three parameter version this can be aBlob
,File
, or aUSVString
. If none of these are specified the value is converted to a string. filename
Optional- The filename reported to the server (a
USVString
), when aBlob
orFile
is passed as the second parameter. The default filename forBlob
objects is "blob".
Note: If you specify a Blob
as the data to append to the FormData
object, the filename that will be reported to the server in the "Content-Disposition" header used to vary from browser to browser.
Example
The following line creates an empty FormData
object:
var formData = new FormData(); // Currently empty
You can set key/value pairs on this using FormData.set
:
formData.set('username', 'Chris'); formData.set('userpic', myFileInput.files[0], 'chris.jpg');
Specifications
Specification | Status | Comment |
---|---|---|
XMLHttpRequest The definition of 'set()' in that specification. |
Living Standard |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 50.0 | 39.0 (39.0) | No support | No support | No support |
Available in web workers | 50.0 | 39.0 (39.0) | No support | No support | No support |
Feature | Android | Android Webview | Firefox Mobile (Gecko) | Firefox OS (Gecko) | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|---|
Basic support | No support | 50.0 | (Yes) | (Yes) | No support |
No support |
No support | 50.0 |
Available in web workers | No support | 50.0 | (Yes) | (Yes) | No support | No support | No support | 50.0 |
See also
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/formdata/set