A simple example of method decorator in Typescript

method_decorator_example.ts

class Greeter {
  @ChangeName('Ammara')
  greet(greeting: string) {
    return "Hello, " + greeting;
  }
}

function ChangeName(value: string) {
  return function (
    target: any,
    propertyKey: string,
    descriptor: PropertyDescriptor
  ) {
    var originalMethod = descriptor.value;
    descriptor.value = function(...args: any) {
      return "Hello, " + value;
    }
    return descriptor;
  };
}

const person = new Greeter();
console.log(person.greet('Alif'));