Save svg from dom as file (great when working with d3)

index.html

<a id="downloadLink" href="" download="diagram.svg">Download ↓</a>
<svg id="svg" width="120" height="120">
        <rect fill="#000000" x="10" y="10" width="100" height="100"></rect>
</svg>

<script type="text/javascript">
setDownloader('downloadLink', 'svg')

function setDownloader(linkId, svgId) {
    // Get svg element
    var svg = document.getElementById(svgId)

    // Get svg source
    var serializer = new XMLSerializer()
    var source = serializer.serializeToString(svg)

    // Add name spaces
    if (!source.match(/^<svg[^>]*?\sxmlns=(['"`])https?\:\/\/www\.w3\.org\/2000\/svg\1/)) {
        source = source.replace(/^<svg/, '<svg xmlns="http://www.w3.org/2000/svg"')
    }
    if (!source.match(/^<svg[^>]*?\sxmlns:xlink=(['"`])http\:\/\/www\.w3\.org\/1999\/xlink\1/)) {
        source = source.replace(/^<svg/, '<svg xmlns:xlink="http://www.w3.org/1999/xlink"')
    }

    // Add xml declaration
    source = '<?xml version="1.0" standalone="no"?>\r\n' + source

    // Convert SVG source to URI data scheme
    var url = "data:image/svg+xml;charset=utf-8," + encodeURIComponent(source)

    // Set url value to a element's href attribute
    document.getElementById(linkId).href = url
}
</script>

I assumed a generic SVG source string, that might contain other quotes. But ( new XMLSerializer() ).serializeToString( svg ) might only produce double-quoted attributes. I'm not sure, you're probably right.