add first version with basic usage

README.md

@@ -1,3 +1,34 @@
 localpubsub
 ===
 
+Simple pubsub lightweight library using Window event listener and storage event.
+
+#### Subscribing
+`subscribe(topic, callbackFunction);`
+
+
+```
+import localpubsub from 'localpubsub';
+
+function displayMessage(data) {
+  console.log(data)
+}
+localpubsub.subscribe('my topic', displayMessage);
+```
+
+#### Publishing
+`publish(topic, message);`
+
+```
+localpubsub.publish('my topic', 'Hello');
+```
+
+#### Unsubscribe
+`unsubscribe(topic);`
+
+```
+const subscription = localpubsub.subscribe(topic, displayMessage);
+subscription.unsubscribe();
+
+localpubsub.unsubscribe(topic);
+```

index.js

@@ -0,0 +1,54 @@
+let topics = {};
+
+function subscribe(topic, listener) {
+  if (!topics.hasOwnProperty(topic)) {
+    topics[topic] = listener;
+  }
+  window.addEventListener(
+    topic,
+    eventData => processCustomEvent(topic, listener, eventData),
+    false
+  );
+  window.addEventListener(
+    "storage",
+    eventData => processStorage(topic, listener, eventData),
+    false
+  );
+  return {
+    unsubscribe: () => {
+      unsubscribe(topic);
+    }
+  };
+}
+
+function processCustomEvent(topic, cb, result) {
+  if (topic === result.type) {
+    return cb({ topic, value: result.detail, eventObject: result });
+  }
+}
+
+function processStorage(topic, cb, result) {
+  if (topic === result.key) {
+    return cb({ topic, value: result.newValue, eventObject: result });
+  }
+}
+
+function publish(eventName, eventValue) {
+  if (topics[eventName]) {
+    window.localStorage.setItem(eventName, eventValue);
+    const customEvent = new CustomEvent(eventName, { detail: eventValue });
+    window.dispatchEvent(customEvent);
+  }
+}
+
+function unsubscribe(subscribeKey) {
+  window.localStorage.removeItem(subscribeKey);
+  delete topics[subscribeKey];
+}
+
+export default {
+  topics,
+  publish,
+  subscribe,
+  unsubscribe
+};