Fix immideate field deleting

DzyubSpirit · DzyubSpirit · commit 2a7571ef5674 · 2018-05-20T22:59:05.000+03:00
PR-URL: #6
diff --git a/JavaScript/7-delete.js b/JavaScript/7-delete.js
@@ -0,0 +1,81 @@
+'use strict';
+
+function Transaction() {}
+
+Transaction.start = (data) => {
+  console.log('\nstart transaction');
+  let delta = {};
+  const deleteDelta = new Set();
+
+  const methods = {
+    commit: () => {
+      console.log('\ncommit transaction');
+      for (const key of deleteDelta) {
+        delete data[key];
+      }
+      Object.assign(data, delta);
+      delta = {};
+    },
+    rollback: () => {
+      console.log('\nrollback transaction');
+      delta = {};
+      deleteDelta.clear();
+    },
+    clone: () => {
+      console.log('\nclone transaction');
+      const cloned = Transaction.start(data);
+      Object.assign(cloned.delta, delta);
+      return cloned;
+    }
+  };
+
+  return new Proxy(data, {
+    get(target, key) {
+      if (key === 'delta') return delta;
+      if (methods.hasOwnProperty(key)) return methods[key];
+      if (delta.hasOwnProperty(key)) return delta[key];
+      return target[key];
+    },
+    getOwnPropertyDescriptor: (target, key) => (
+      Object.getOwnPropertyDescriptor(
+        delta.hasOwnProperty(key) ? delta : target, key
+      )
+    ),
+    ownKeys() {
+      const changes = Object.keys(delta);
+      const keys = Object.keys(data).concat(changes);
+      return keys.filter((x, i, a) => a.indexOf(x) === i);
+    },
+    set(target, key, val) {
+      console.log('set', key, val);
+      if (target[key] === val) delete delta[key];
+      else delta[key] = val;
+      deleteDelta.delete(key);
+      return true;
+    },
+    deleteProperty(target, prop) {
+      if (deleteDelta.has(prop)) return false;
+      deleteDelta.add(prop);
+      return true;
+    },
+  });
+};
+
+// Usage
+
+const data = { name: 'Marcus Aurelius', born: 121 };
+
+const transaction = Transaction.start(data);
+console.dir({ data });
+
+transaction.city = 'Beijing';
+delete transaction.born;
+
+console.dir({
+  keys: Object.keys(transaction),
+  delta: transaction.delta
+});
+
+console.dir({ data });
+transaction.commit();
+console.dir({ data });
