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.
There are two versions of this method: a two and a three parameter version:
formData.set(name, value); formData.set(name, value, filename);
name
value
.value
USVString
, or if it is not, it is converted to a string. In the three parameter version this can be a Blob
, File
, or a USVString
. If none of these are specified the value is converted to a string.filename
Optional
USVString
), when a Blob
or File
is passed as the second parameter. The default filename for Blob
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.
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');
Specification | Status | Comment |
---|---|---|
XMLHttpRequest The definition of 'set()' in that specification. | Living Standard |
Desktop | ||||||
---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | |
Basic support | 50 | No | 39 | No | No | Yes |
Mobile | |||||||
---|---|---|---|---|---|---|---|
Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | iOS Safari | Samsung Internet | |
Basic support | ? | 50 | No | Yes | No | No | ? |
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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/FormData/set