Performance improvement for attribute patching: (#257)

* Performance improvements for attribute patching:
- Avoid call to split and use a object lookup instead
- Simplify the code for `svg` name spaced attributes

* Fix typo and added missing property

* Fixing previous attribute ns assignment

* Refactor NS

* Add fast path for non namespaced elements

* Adding tests

src/modules/attributes.ts

@@ -1,10 +1,6 @@
 import {VNode, VNodeData} from '../vnode';
 import {Module} from './module';
 
-const NamespaceURIs = {
-  "xlink": "http://www.w3.org/1999/xlink"
-};
-
 const booleanAttrs = ["allowfullscreen", "async", "autofocus", "autoplay", "checked", "compact", "controls", "declare",
                 "default", "defaultchecked", "defaultmuted", "defaultselected", "defer", "disabled", "draggable",
                 "enabled", "formnovalidate", "hidden", "indeterminate", "inert", "ismap", "itemscope", "loop", "multiple",
@@ -12,6 +8,10 @@ const booleanAttrs = ["allowfullscreen", "async", "autofocus", "autoplay", "chec
                 "required", "reversed", "scoped", "seamless", "selected", "sortable", "spellcheck", "translate",
                 "truespeed", "typemustmatch", "visible"];
 
+const xlinkNS = 'http://www.w3.org/1999/xlink';
+const xmlNS = 'http://www.w3.org/XML/1998/namespace';
+const colonChar = 58;
+const xChar = 120;
 const booleanAttrsDict: {[attribute: string]: boolean} = Object.create(null);
 
 for (let i = 0, len = booleanAttrs.length; i < len; i++) {
@@ -21,7 +21,7 @@ for (let i = 0, len = booleanAttrs.length; i < len; i++) {
 function updateAttrs(oldVnode: VNode, vnode: VNode): void {
   var key: string, elm: Element = vnode.elm as Element,
       oldAttrs = (oldVnode.data as VNodeData).attrs,
-      attrs = (vnode.data as VNodeData).attrs, namespaceSplit: Array<string>;
+      attrs = (vnode.data as VNodeData).attrs;
 
   if (!oldAttrs && !attrs) return;
   if (oldAttrs === attrs) return;
@@ -40,9 +40,14 @@ function updateAttrs(oldVnode: VNode, vnode: VNode): void {
           elm.removeAttribute(key);
         }
       } else {
-        namespaceSplit = key.split(":");
-        if (namespaceSplit.length > 1 && NamespaceURIs.hasOwnProperty(namespaceSplit[0])) {
-          elm.setAttributeNS((NamespaceURIs as any)[namespaceSplit[0]], key, cur);
+        if (key.charCodeAt(0) !== xChar) {
+          elm.setAttribute(key, cur);
+        } else if (key.charCodeAt(3) === colonChar) {
+          // Assume xml namespace
+          elm.setAttributeNS(xmlNS, key, cur);
+        } else if (key.charCodeAt(5) === colonChar) {
+          // Assume xlink namespace
+          elm.setAttributeNS(xlinkNS, key, cur);
         } else {
           elm.setAttribute(key, cur);
         }

test/htmldomapi.js

@@ -2,7 +2,9 @@ var assert = require('assert');
 
 var snabbdom = require('../snabbdom');
 var h = require('../h').default;
-var patch = snabbdom.init([]);
+var patch = snabbdom.init([
+  require('../modules/attributes').default
+]);
 
 describe('svg', function () {
  var elm, vnode0;
@@ -10,6 +12,7 @@ describe('svg', function () {
    elm = document.createElement('svg');
    vnode0 = elm;
  });
+
  it('removes child svg elements', function(){
    var a = h('svg', {}, [
     h('g'),
@@ -21,4 +24,30 @@ describe('svg', function () {
    var result = patch(patch(vnode0, a), b).elm;
    assert.equal(result.childNodes.length, 1); 
  });
+
+ it('adds correctly xlink namespaced attribute', function(){
+   var xlinkNS = 'http://www.w3.org/1999/xlink';
+   var testUrl = '/test';
+   var a = h('svg', {}, [
+     h('use', {
+       attrs: { 'xlink:href': testUrl }
+     }, [])
+   ]);
+
+   var result = patch(vnode0, a).elm;
+   assert.equal(result.childNodes.length, 1);
+   assert.equal(result.childNodes[0].getAttribute('xlink:href'), testUrl); 
+   assert.equal(result.childNodes[0].getAttributeNS(xlinkNS,'href'), testUrl);
+
+ });
+
+ it('adds correctly xml namespaced attribute', function(){
+   var xmlNS = 'http://www.w3.org/XML/1998/namespace';
+   var testAttrValue = 'und';
+   var a = h('svg', { attrs: { 'xml:lang': testAttrValue } }, []);
+
+   var result = patch(vnode0, a).elm;
+   assert.equal(result.getAttributeNS(xmlNS, 'lang'), testAttrValue);
+   assert.equal(result.getAttribute('xml:lang'), testAttrValue); 
+ });
 })