Add decorators.ts

decorators.ts

@@ -0,0 +1,54 @@
+// Class decorator
+function seal(constructor: Function) {
+  Object.seal(constructor);
+  Object.seal(constructor.prototype);
+}
+
+// Method decorator
+function setTimeout(ms = 0) { // Notice the wrapper function to get arguments, this can be done to any decorator function
+  return function(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
+    const originalMethod = descriptor.value;
+    descriptor.value = function () {
+      setTimeout(() => originalMethod.apply(this, arguments), ms);
+    };
+    return descriptor;
+  }
+}
+
+// Accessor/Property decorator
+function log(target: any, key: string) {
+  let value = target[key];
+
+  Object.defineProperty(target, key, {
+    get: () => {
+      console.log(`Get => ${key}`);
+      return value;
+    },
+    set: (newValue) => {
+      console.log(`Set: ${key} => ${e}`);
+      value = newValue;
+    },
+    enumerable: true,
+    configurable: true
+  });
+}
+
+// Example
+@seal
+class Person { 
+  @log firstName: string;
+  @log lastName: string;
+
+  @log 
+  get name() { return `${this.firstName} ${this.lastName}`};
+
+  constructor(firstName: string, lastName: string) { 
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
+  @timeout(1000)
+  whoami() {
+    return this.name;
+  }
+}