How to set up camera.up in three.js and read the document?

  node.js, question

Seeing this code, I don’t know what this code really means. Who knows?

Because the assignment [x,y,x]===[0,0,1], that is to say, the upward direction of the camera is the direction of the z-axis. Simply understood as the rotation angle of the camera.
If [x,y,x]===[1,0,0] is assigned, then the camera’s upward direction is the x-axis direction, and the “photo” taken is erected.