Check for misspelled JavaScript keywords

Is your feature request related to a problem? Please describe.

The other day in a Code Nation classroom, a student had written out a simple jQuery function, but their code wasn’t working. One of the teachers couldn’t see anything wrong, and thought maybe popcode wasn’t working. Eventually, I spotted the problem: the word function was misspelled, I think as fucntion or some reversal of two letters.

Describe the solution you'd like

A small solution would be adding a specific check for misspellings of function, perhaps in contexts where we could deduce the intended word.

A bigger scope but possibly a better solution would be a code “spellchecker,” which would be super helpful in cases like this. Simple typing/spelling errors where key words are off by one letter are super common, especially for beginners (but possible for anyone and hard to debug). Other common issues are missed capitalization or hyphenation, and I believe we should try to capture these if possible, as well.

Start by locating the editor's JavaScript parsing or error-reporting entry point and review how invalid keywords are surfaced; the issue names no file or test. Define the supported misspelling cases, beginning with function, and add coverage so the editor reports them without treating unrelated identifiers as keywords.