Store best score in localStorage

Dependency injection and hide best score for incompatible browsers

js/local_score_manager.js

@@ -0,0 +1,24 @@
+function LocalScoreManager() {
+  this.key = 'bestScore';
+}
+
+LocalScoreManager.prototype.get = function () {
+  if (!this.isSupported()) {
+    return 0;
+  }
+
+  return localStorage.getItem(this.key);
+};
+
+LocalScoreManager.prototype.set = function (score) {
+  if (!this.isSupported()) {
+    return false;
+  }
+
+  localStorage.setItem(this.key, score);
+};
+
+LocalScoreManager.prototype.isSupported = function () {
+  return !!window.localStorage;
+};
+