Convert CANVAS data to binary data and then to a filename using a Blob

imagedata-to-filename.js

function binaryblob(){
	var byteString = atob(document.querySelector("canvas").toDataURL().replace(/^data:image\/(png|jpg);base64,/, ""));
	var ia = new Uint8Array(ab);
	for (var i = 0; i < byteString.length; i++) {
        ia[i] = byteString.charCodeAt(i);
    }
    var dataView = new DataView(ab);
	var blob = new Blob([dataView], {type: "image/png"});
	var DOMURL = self.URL || self.webkitURL || self;
	var newurl = DOMURL.createObjectURL(blob);

	var img = '<img src="'+newurl+'">'; 
  d3.select("#img").html(img);
}

Can I ask you a question? What is "ab" mean?

I think it means ArrayBuffer, I assumed it was missing this step:

let ab = new ArrayBuffer(byteString.length);