Going from Arabic (MSA) to Javanese (Basa Jawa) has a composite linguistic distance of 87% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Arabic → Latin/Javanese
Afro-Asiatic ↔ Austronesian
The 5 languages with the lowest linguistic distance from Arabic (MSA):
A quick 3-question check between Arabic (MSA) and Javanese. No signup.