FormData

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

Note: This feature is available inWeb Workers.

TheFormData interface provides a way to construct a set of key/value pairs representing form fields and their values, which can be sent using thefetch(),XMLHttpRequest.send() ornavigator.sendBeacon() methods. It uses the same format a form would use if the encoding type were set to"multipart/form-data".

You can also pass it directly to theURLSearchParams constructor if you want to generate query parameters in the way a<form> would do if it were using simpleGET submission.

An object implementingFormData can directly be used in afor...of structure, instead ofentries():for (const p of myFormData) is equivalent tofor (const p of myFormData.entries()).

Constructor

FormData(): Creates a newFormData object.

Instance methods

FormData.append(): Appends a new value onto an existing key inside aFormData object, or adds the key if it does not already exist.
FormData.delete(): Deletes a key/value pair from aFormData object.
FormData.entries(): Returns aniterator that iterates through all key/value pairs contained in theFormData.
FormData.get(): Returns the first value associated with a given key from within aFormData object.
FormData.getAll(): Returns an array of all the values associated with a given key from within aFormData.
FormData.has(): Returns whether aFormData object contains a certain key.
FormData.keys(): Returns aniterator iterates through all keys of the key/value pairs contained in theFormData.
FormData.set(): Sets a new value for an existing key inside aFormData object, or adds the key/value if it does not already exist.
FormData.values(): Returns aniterator that iterates through all values contained in theFormData.