TypeError: x is not a constructor
This error appears when you try to use code which does not have an PsychoJS equivalent. You need to try a different approach.
For example, if you have created a countdown timer, you just need to define the clock in a Both code component (probably the Begin Experiment tab) and edit the JavaScript side.
myClock = core.CountdownTimer(60) # Python
myClock = new util.CountdownTimer(60); // JavaScript
Once defined you can use myClock.reset() and myClock.getTime() as normal.
On the other hand, if you have used visual.Circle in a code component and get TypeError: visual.Circle is not a constructor use visual.ShapeStim instead.
visual.ShapeStim(
win=win,
fillColor='white',
lineColor='white',
vertices=[[0.000,0.866], [0.091,0.861], [0.180,0.847], [0.268,0.824], [0.352,0.791], [0.433,0.750], [0.509,0.701], [0.579,0.644], [0.644,0.579], [0.701,0.509], [0.750,0.433], [0.791,0.352], [0.824,0.268], [0.847,0.180], [0.861,0.091], [0.866,0.000], [0.861,-0.091], [0.847,-0.180], [0.824,-0.268], [0.791,-0.352], [0.750,-0.433], [0.701,-0.509], [0.644,-0.579], [0.579,-0.644], [0.509,-0.701], [0.433,-0.750], [0.352,-0.791], [0.268,-0.824], [0.180,-0.847], [0.091,-0.861], [0.000,-0.866], [-0.091,-0.861], [-0.180,-0.847], [-0.268,-0.824], [-0.352,-0.791], [-0.433,-0.750], [-0.509,-0.701], [-0.579,-0.644], [-0.644,-0.579], [-0.701,-0.509], [-0.750,-0.433], [-0.791,-0.352], [-0.824,-0.268], [-0.847,-0.180], [-0.861,-0.091], [-0.866,0.000], [-0.861,0.091], [-0.847,0.180], [-0.824,0.268], [-0.791,0.352], [-0.750,0.433], [-0.701,0.509], [-0.644,0.579], [-0.579,0.644], [-0.509,0.701], [-0.433,0.750], [-0.352,0.791], [-0.268,0.824], [-0.180,0.847], [-0.091,0.861]],
pos = [0,0],
depth = 50,
size=.3,
opacity = 1
)