The ornamental design for a holder for electronicdevices, as shown and described.
1.-4. Holder for electronic devices
2. 2.1 is a rear perspective view of a holder for electronic devices, showing our new design, in an unfolded position, shown in a condition of use;
2.2 is a side view thereof, shown in an unfolded position;
2.3 is a rear view thereof, shown in an unfolded position;
2.4 is a rear view thereof, shown in a folded position;
2.5 is a side view thereof, shown in a folded position; and
2.6 is a top view thereof, shown in a folded position.
3. The broken lines depict portions of the holder for electronic devices that form no part of the claimed design. The broken lines in reproduction 2.1 depicting an electronic device are included for the purpose of illustrating a condition of use and form no part of the claimed design.