1. XMLHttpRequest advanced features

    Adds more functionality to XHR (aka AJAX) requests like file uploads, transfer progress information and the ability to send form data. Previously known as [XMLHttpRequest Level 2](https://www.w3.org/TR/2012/WD-XMLHttpRequest-20120117/), these features now appear simply in the XMLHttpRequest spec.

  2. formdata api

  3. formdataevent api

  4. formdataevent api: formdata

  5. formdataevent api: `formdataevent()` constructor

  6. formdata api: @@iterator

  7. formdata api: append

  8. formdata api: append: `filename` parameter

  9. formdata api: delete

  10. formdata api: entries

  11. formdata api: foreach

  12. formdata api: `formdata()` constructor

  13. formdata api: get

  14. formdata api: getall

  15. formdata api: has

  16. formdata api: keys

  17. formdata api: set

  18. formdata api: values

  19. formdata api: available in workers

  20. htmlformelement api: `formdata` event

  21. navigateevent api: formdata

  22. request api: formdata

  23. response api: formdata

  24. xmlhttprequest api: send: formdata as parameter to send()