Download attribute not working in safari

try this code:

var element = document.createElement('a');
            var clearUrl = base64.replace(/^data:image\/\w+;base64,/, '');

            // element.setAttribute('href', 'data:attachment/image' + base64);
            element.setAttribute('href', 'data:application/octet-stream;base64,' + encodeURIComponent(clearUrl));
            element.setAttribute('download', 'filename.jpg');
            document.body.appendChild(element);
            element.click();
            document.body.removeChild(element)

This is work for me in safari version 10.0.3

According to https://developer.apple.com/library/content/releasenotes/General/WhatsNewInSafari/Articles/Safari_10_1.html, it was added in Safari 10.1:

HTML5 Download Attribute The download attribute for anchor elements indicates that the link target is a download link that downloads a file, instead of a navigational link. When you click a a link with the download attribute, the target is downloaded as a file. Optionally, the value of the download attribute provides the suggested name of the file.

It doesn't seem to be available in iOS Safari 11.1 though from my own testing, which has me a bit confused. I'd expect them to be equal in standards support, based on their similar version numbering.