function _addToZip(zip, obj) {
	if (_ieExcel === undefined) {
		// Detect if we are dealing with IE's _awful_ serialiser by seeing if it
		// drop attributes
		_ieExcel =
			_serialiser
				.serializeToString(
					new window.DOMParser().parseFromString(
						excelStrings['xl/worksheets/sheet1.xml'],
						'text/xml'
					)
				)
				.indexOf('xmlns:r') === -1;
	}

	$.each(obj, function (name, val) {
		if ($.isPlainObject(val)) {
			var newDir = zip.folder(name);
			_addToZip(newDir, val);
		}
		else {
			if (_ieExcel) {
				// IE's XML serialiser will drop some name space attributes from
				// from the root node, so we need to save them. Do this by
				// replacing the namespace nodes with a regular attribute that
				// we convert back when serialised. Edge does not have this
				// issue
				var worksheet = val.childNodes[0];
				var i, ien;
				var attrs = [];

				for (i = worksheet.attributes.length - 1; i >= 0; i--) {
					var attrName = worksheet.attributes[i].nodeName;
					var attrValue = worksheet.attributes[i].nodeValue;

					if (attrName.indexOf(':') !== -1) {
						attrs.push({ name: attrName, value: attrValue });

						worksheet.removeAttribute(attrName);
					}
				}

				for (i = 0, ien = attrs.length; i < ien; i++) {
					var attr = val.createAttribute(
						attrs[i].name.replace(':', '_dt_b_namespace_token_')
					);
					attr.value = attrs[i].value;
					worksheet.setAttributeNode(attr);
				}
			}

			var str = _serialiser.serializeToString(val);

			// Fix IE's XML
			if (_ieExcel) {
				// IE doesn't include the XML declaration
				if (str.indexOf('<?xml') === -1) {
					str =
						'<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' +
						str;
				}

				// Return namespace attributes to being as such
				str = str.replace(/_dt_b_namespace_token_/g, ':');

				// Remove testing name space that IE puts into the space preserve attr
				str = str.replace(/xmlns:NS[\d]+="" NS[\d]+:/g, '');
			}

			// Safari, IE and Edge will put empty name space attributes onto
			// various elements making them useless. This strips them out
			str = str.replace(/<([^<>]*?) xmlns=""([^<>]*?)>/g, '<$1 $2>');

			zip.file(name, str);
		}
	});
}
Recursively add XML files from an object's structure to a ZIP file. This
allows the XSLX file to be easily defined with an object's structure matching
the files structure.

@param {JSZip} zip ZIP package
@param {object} obj Object to add (recursive)