How to add comma between array items?

How can I add a comma between the values, when using map function to print out all the values? (Using React, that's why I have the key etc.)

{ cars.map(car => {
    return(
      <p key={car.id}>{car.title} ,</p>
    );
}); }

This is how I would like the result to be, with no comma in the end of the last array item:

Audi, Nissan, Mazda, Toyota

Should I do it somehow like this?

{ cars.map((car, index) => {
  const separator = ", ";
  if(index === car.length - 1) {
     return(
       <p key={car.id}>{car.title} + separator </p>
     );
  }
}); 
}