JavaScript Formdata_basics Guide
FormData captures form fields for easy AJAX submission. Supports file uploads and multipart data. The guide walks through FormData API. `const fd = new FormData(formElement)`. For each field: name and value. `fd.get("fieldName")` — single value. `fd.getAll("fieldName")` — multiple (checkboxes). `fd.append(key, value)` — add. `fd.delete(key)` — remove. `fd.has(key)` — check. Send as POST with fetch/XMLHttpRequest. Content-Type set automatically to multipart/form-data for files. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.