Limitations and traps

Forms you didn’t write

obfo never evaluates, renders or fetches anything: it reads value, checked, files and text, and builds plain objects and arrays. It doesn’t validate anything either. A form whose markup comes from someone else can still:

• choose every key, including constructor, toString and __proto__. A field named __proto__ becomes an ordinary own property (obfo defines keys rather than assigning them), so it can’t replace the result’s prototype; other surprising keys are yours to reject.
• choose every value, regardless of required, pattern, min, max or maxlength. Check the result, or call form.reportValidity() before reading.
• throw. A missing key, a bigint cast on non-integer text or a file cast on a text input throws; with observe, pass onError. Containers are read recursively, so thousands of nested containers throw a RangeError.

What isn’t read

• Custom form-associated elements (ElementInternals) and contenteditable regions without data-obfo-value. Only input, textarea, select and data-obfo-value elements carry values.
• Inputs outside the element, even ones associated with the form through their form attribute.
• Nothing is skipped for being disabled (unlike FormData): a disabled input is read like any other.

What fill and observe can’t do

• fill skips file inputs and checkboxes or radios read without a boolean cast, and never adds or removes elements. See Writing a form.
• observe hears events, not property writes, and reads structure changes only on the next event. See Live values.

Testing without a browser

obfo uses no DOM globals (element kinds come from localName; Event and timers from the element’s own window), so it runs under Node against happy-dom without installing anything on globalThis. Its own suite does exactly that, and three differences from a browser matter when you test code built on it:

• Events are synchronous. happy-dom runs no microtasks between an input and a change dispatched from a test, so a test can’t show the double call a microtask-based coalescer made in a real browser. obfo’s Playwright suite (Chromium, Firefox, WebKit) is where that was found.
• innerText keeps whitespace a browser collapses, so data-obfo-value text differs.
• No file picker. Set files with new window.DataTransfer() and input.files = transfer.files.