Onclick save drawing for Javascript in <script> element [duplicate]

Question

 function save() {
    document.getElementById("canvasimg").style.border = "2px solid";
    var dataURL = canvas.toDataURL();
    document.getElementById("canvasimg").src = dataURL;
    document.getElementById("canvasimg").style.display = "inline";
}

wich will creat a new picture to the right but i want it to download right away i think you would have to use

<a href="x" download>

but what would x be for the download and how would i set it to download on click

The Comment

Does this answer your question? Download data URL file – Harshit Rastogi

i tried to use that code but it says it has an error trying to download im using github so i think it tried to download the site i made. The error in the bottom right

here is the website ive been trying for it to work its a little messy but in the middle is the drawing https://bobzilla07.github.io/web-platform-j1pnv3/