类装饰器

function log(prefix?: string) {
  return (target) => {
    // save a reference to the original constructor
    var original = target;
    // a utility function to generate instances of a class
    function construct(constructor, args) {
      var c: any = function () {
        return constructor.apply(this, args);
      }
      c.prototype = constructor.prototype;
      return new c();
    }
    // the new constructor behavior
    var f: any = function (...args) {
      console.log(prefix + original.name);
      return construct(original, args);
    }
    // copy prototype so instanceof operator still works
    f.prototype = original.prototype;
    // return new constructor (will override original)
    return f;
  };
}
@log('hello')
class World {
}
const w = new World(); // outputs "helloWorld"