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.
set(name, value)
set(name, value, filename)
Parameters
-
name
-
The name of the field whose data is contained in value
.
-
value
-
The field's value. This can be a USVString
or Blob
(including subclasses such as File
). If none of these are specified the value is converted to a string.
-
filename
Optional
-
The filename reported to the server (a USVString
), when a Blob
or File
is passed as the second parameter. The default filename for Blob
objects is "blob". The default filename for File
objects is the file's filename.
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();
You can set key/value pairs on this using FormData.set
:
formData.set('username', 'Chris');
formData.set('userpic', myFileInput.files[0], 'chris.jpg');
If the sent value is different than String or Blob it will be automatically converted to String:
formData.set('name', 72);
formData.get('name');