Using jessiecode to update jsxgraph objects

Question

I'm trying to use jessiecode to update canvas objects. Looks like I'm missing something here - fiddleboard.create('circle', [p1, 2.0],{visible:board.jc.snippet("counter < 5 || counter > 10", true, 'counter', false)}); and board.create('text',[1,1,board.jc.snippet(counter,true,'counter',false)]);

In this fiddle, the circle's visible property and text at 1,1 doesn't change on clicking button.

Answer 1

This is indeed a challenge! The main problem here is that JessieCode is not allowed to access JavaScript variables. This is by design: for security reasons access to the DOM has to be prevented.

That means, counter has to be a JessieCode variable. Arbitrary JessieCode code can be executed with board.jc.parse("code").
Here is the complete example see http://jsfiddle.net/a3x5de6t/4/:

var board = JXG.JSXGraph.initBoard('jxgbox', {
    axis: true
});

// Set JessieCode variable `counter`
board.jc.parse("counter = 0;");

var p1 = board.create('point', [-2.0, 2.0]);

// Create `function() {return (counter < 5 || counter > 10) ? true: false; }`
var c1 = board.create('circle', [p1, 2.0],{visible: board.jc.snippet(
        "(counter < 5 || counter > 10) ? true: false", true, '', false)});

// Increase JessieCode variable `counter`
var button = board.create('button',[1, 4, 'increase counter',
    function() {
        board.jc.parse('counter = counter + 1;');
    }
]);

// Create function `function() {return counter; }` 
var t = board.create('text',[1, 1, board.jc.snippet('counter' , true, '', )]);

Best wishes, Alfred