Button

In my slide show I have HTML5 canvas and there I have a button that changes an image but when you press the button
then nothing happens on the first press but the second press so it happens the image is displayed.
I want it to happen on the first print.
Here is the code:
this.button.addEventListener("click", Toggle3.bind(this));
var on = 0;
this.nr60b_btn.visible = false;
this.nr60a_btn.visible = false;
function Toggle3() {
if (on == 0) {
this.nr60b_btn.visible = true;
this.nr60a_btn.visible = true;
this.stop();
on = 1;
} else {
this.nr60b_btn.visible = false;
this.nr60a_btn.visible = false;
on = 0;
}
}