FormData: append() method

Syntax

append(name, value)
append(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 string 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 string), 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.

Return value

None (undefined).

Examples

formData.append("username", "Chris");

When the value is a Blob (or a File), you can specify its name with the filename parameter:

formData.append("user-pic", myFileInput.files[0], "chris.jpg");

As with regular form data, you can append multiple values with the same name:

formData.append("user-pic", myFileInput.files[0], "chris1.jpg");
formData.append("user-pic", myFileInput.files[1], "chris2.jpg");

If the value is not a string or a Blob, append() will convert it to a string automatically:

formData.append("name", true);
formData.append("name", 72);
formData.getAll("name"); // ["true", "72"]

Specifications

Browser compatibility

See also

• Using FormData objects
• <Form>