The ornamental design for an electronicwhiteboard, as shown and described.
1. Electronic whiteboard
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 :Top
1.7 : Bottom
1.8 : Reference
1.9 : Reference view 2
The broken lines depict portions of the electronic whiteboard that form no part of the claimed design; reproduction 1.1 is a front perspective view of the electronic whiteboard; reproduction 1.2 is a front view thereof; reproduction 1.3 is a back view thereof; reproduction 1.4 is a left view thereof; reproduction 1.5 is a right view thereof; reproduction 1.6 is a top view thereof; reproduction 1.7 is a bottom view thereof; reproduction 1.8 is a reference view showing an example of a state in which the display part is rotated in the vertical direction, and forms no part of the claimed design; reproduction 1.9 is a reference view showing that a camera can be installed in the upper center of the front and the height of the display can be adjusted up and down, and forms no part of the claimed design; this is a design for an electronic whiteboard with a display part that can be rotated in the vertical direction as shown in reproduction 1.8; as shown in reproduction 1.9, a camera can be installed at the upper center of the front, and the height can be adjusted up and down.