Reset camera using OrbitControls.js

You can reset the camera when using OrbitControls like so:

controls.reset();

three.js r.71

Pan operation is updating vector called this.center , you need to reset it to see pan method ,

this.center.add( distance );

set this method to:

this.resetCamera = function ( ) {
        this.object.position.x= camera_initial_position.xPosition;
        this.object.position.y = camera_initial_position.yPosition;
        this.object.position.z = camera_initial_position.zPosition;
        this.center.x= camera_initial_target.x;
        this.center.y= camera_initial_target.y;
        this.center.z= camera_initial_target.z;
    };

and then the update method will keep the camera looking at the center vector.