JavaScript can change the pieces on the board only if they are represented by individual images. But the PNG rendering method does not use individual piece images. It displays the whole diagram as a single image like the Diagram Designer does. In many cases, such as this one, all you have to do is change the rendering method to either Table or CSS, and then you can use JavaScript to display past moves without reloading the page for each move.
JavaScript can change the pieces on the board only if they are represented by individual images. But the PNG rendering method does not use individual piece images. It displays the whole diagram as a single image like the Diagram Designer does. In many cases, such as this one, all you have to do is change the rendering method to either Table or CSS, and then you can use JavaScript to display past moves without reloading the page for each move.