Stepper Motor Spinning Slow

We know that software is never bug free... but it is of great relieve - I'm sure for @fobus - that hardware isn't perfect either... ;-) and the scope where to find the cause for an issues has to include that.

@fobus' key element is the setup for this extremely terse version of interval callback (paraphrased from stp):

// stp - step
var step = function() { digitalWrite(pins,  steps[ stepIdx = ++stepIdx % 8 ]); };