Point 'fixed' in one direction

`A` and `B` are free points. Whenever the board is updated, e.g. after a drag event, the x-coordinate of `A` is set to 1 and the y-coordinate of `B` is set to 1. Therefore, `A` moves on a vertical line, `B` moves on a horizontal line.

The JavaScript code

var brd = JXG.JSXGraph.initBoard('jxgbox',{axis:true,boundingbox:[-1,2,2,-1]});

var A = brd.create('point', [1,0]);
var B = brd.create('point', [0,1]);

brd.on('update', function(){
        A.moveTo([1, A.Y()]);
        B.moveTo([B.X(), 1]);
});