Step function

The underlying JavaScript code

var board = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-5,8,8,-5], axis:true});

var f = function(x) {
  if(x<0)
    return -1;
  if(x>=0 && x <2)
    return 1;
  if(x>=2)
    return 2;
}
board.create('functiongraph',[f]);