Fully implement the FormData API
Currently the FormData API is only partially implemented in Edge. Most of the more useful methods are missing including: has(), get(), set(), delete(), entries(), and many others.
FormData is already fully implemented on the other major browsers (Firefox, Chrome, Safari) - see: https://developer.microsoft.com/en-us/microsoft-edge/platform/catalog/?q=formdata
The FormData interface provides a way to easily construct a set of key/value pairs representing form fields and their values, which can then be easily sent using the XMLHttpRequest.send() method. It uses the same format a form would use if the encoding type were set to "multipart/form-data".
An object implementing FormData can directly be used in a for...of structure, instead of entries(): for (var p of myFormData) is equivalent to for (var p of myFormData.entries()).