A touchscreen for an electronic device includes a first substrate, a second substrate opposite to the first substrate, and photosensors disposed on the first substrate. The second substrate includes a first surface and a second surface opposite to the first surface. When a first light at a first wavelength enters the second substrate via the second surface, the second substrate emits the first light at the first wavelength from the first surface. The second substrate further totally reflects the first light at a second wavelength. The plurality of photosensors detect the first light at the first wavelength penetrating through the second substrate, and output corresponding detecting signals.