FormData: set() method
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 append() is that if the specified key does already exist, set() will overwrite all existing values with the new one, whereas append() will append the new value onto the end of the existing set of values.
Note: This method is available in Web Workers.
Syntax
js
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 string or
Blob(including subclasses such asFile). If none of these are specified the value is converted to a string. filenameOptional-
The filename reported to the server (a string), when a
BloborFileis passed as the second parameter. The default filename forBlobobjects is "blob". The default filename forFileobjects 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.
Return value
None (undefined).
Examples
js
formData.set("username", "Chris");
When the value is a Blob (or a File), you can specify its name with the filename parameter:
js
formData.set("userpic", myFileInput.files[0], "chris.jpg");
If the value is not a string or a Blob, set() will convert it to a string automatically:
js
formData.set("name", 72);
formData.get("name"); // "72"
Specifications
| Specification |
|---|
| XMLHttpRequest Standard # dom-formdata-set |
Browser compatibility
BCD tables only load in the browser