cache DOMParser instance on svg utils module object

- to not have to instantiate one on every appendSVG call

Author: etpinard

src/lib/svg_text_utils.js

@@ -17,6 +17,17 @@ var Lib = require('../lib');
 var xmlnsNamespaces = require('../constants/xmlns_namespaces');
 var stringMappings = require('../constants/string_mappings');
 
+exports.getDOMParser = function() {
+    if(exports.domParser) {
+        return exports.domParser;
+    } else if(window.DOMParser) {
+        exports.domParser = new window.DOMParser();
+        return exports.domParser;
+    } else {
+        throw new Error('Cannot initialize DOMParser');
+    }
+};
+
 // Append SVG
 
 d3.selection.prototype.appendSVG = function(_svgString) {
@@ -27,8 +38,9 @@ d3.selection.prototype.appendSVG = function(_svgString) {
         '</svg>'
     ].join('');
 
-    var dom = new DOMParser().parseFromString(skeleton, 'application/xml'),
-        childNode = dom.documentElement.firstChild;
+    var domParser = exports.getDOMParser();
+    var dom = domParser.parseFromString(skeleton, 'application/xml');
+    var childNode = dom.documentElement.firstChild;
 
     while(childNode) {
         this.node().appendChild(this.node().ownerDocument.importNode(childNode, true));