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 in Web Workers.

The FormData interface provides a way to construct a set of key/value pairs representing form fields and their values, which can be sent using the fetch(), XMLHttpRequest.send() or navigator.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 the URLSearchParams constructor if you want to generate query parameters in the way a <form> would do if it were using simple GET submission.

An object implementing FormData can directly be used in a for...of structure, instead of entries(): for (const p of myFormData) is equivalent to for (const p of myFormData.entries()).

Constructor

FormData(): Creates a new FormData object.

Instance methods

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