physics2D.setJointLimitOn

physics2D.setJointLimitOn sets JointLimitOn on a physics2D object. It takes id, min and max.

physics2D.setJointLimitOn(id, min, max)

function update(dt) {  physics2D.setJointLimitOn('main', 0, 1);}

physics2D.setJointLimitOn is called with values of the shape its signature asks for. The code sits in update(dt), which the engine calls every frame: dt is the time since the last one, in seconds.