var list = [ { id : 0, firstName : 'Chairul', lastName : 'Umam' }, { id : 1, firstName : 'Steven', lastName : 'Gerrard' } ]; var i = list.findIndex(function(x) { return JSON.stringify({ id : x.id, lastName : x.lastName }) == JSON.stringify({ id : 1, lastName : 'Gerrard' }); }); console.log(i);