In Spanish, the pronunciation is khah-BIEHR, with a diphthong. The sound of Spanish J is usually represented with a KH and it's more or less the same sound of CH in German
or in Scottish "loch".
In Basque (Xabier
) is pronounced shah-bee-EHR.
In some old Spanish documents, Javier
is spelled Xavier
), because some centuries ago the X had a sound [kh] (it is the same raison of some X in place names as México, Oaxaca, or in surnames as Ximénez, Mexías). But nowadays, the only correct form of the name in Spanish is Javier