// Aktueller Bildindex (beim Start 0) var current_index = 0; // Bilderwechsel durchführen function switch_image(direction) { var count = images.length; current_index += (direction ? 1 : -1); if (current_index == count) { current_index = 0; } else if (current_index < 0) { current_index = count - 1; } document.getElementById('bilder').src = images[current_index]; }