How to import/use Reflect in typescript

Question

I'm trying to use the code in this SO answer. It uses Reflect. Here's a copy:

export function CustomComponent(annotation: any) {
  return function (target: Function) {
    var parentTarget = Object.getPrototypeOf(target.prototype).constructor;
    var parentAnnotations = Reflect.getMetadata('annotations', parentTarget);

    var parentAnnotation = parentAnnotations[0];
    Object.keys(parentAnnotation).forEach(key => {
      if (isPresent(parentAnnotation[key])) {
        annotation[key] = parentAnnotation[key];
      }
    });
    var metadata = new ComponentMetadata(annotation);

    Reflect.defineMetadata('annotations', [ metadata ], target);
  }
}

First, I got these two errors:

Property 'getMetadata' does not exist on type 'typeof Reflect'.
Property 'defineMetadata' does not exist on type 'typeof Reflect'.

Then I ran npm install reflect-metadata, but I don't know how to use it.

import { Reflect } from reflect-metadata;

Module '".../node_modules/reflect-metadata/index"' has no exported
member 'Reflect'.

Or

import { Reflect } from 'reflect-metadata/Reflect';

Cannot find name 'Record'. 
Type '{}' is not assignable to type 'V'.
File '.../node_modules/reflect-metadata/Reflect.ts' is not a module.

Or

import "reflect-metadata"

rollup: Treating 'fs' as external dependency 
bundle update failed: Error transforming .../node_modules/typescript/lib/typescript.js
with 'commonjs' plugin: The keyword 'package' is reserved (57066:28) in
.../node_modules/typescript/lib/typescript.js 

Or

var reflect = require("reflect-metadata");

Cannot find name 'require'.

Or

declare var require: any;
var reflect = require("reflect-metadata");
var Reflect = reflect.Reflect;

    rollup: Treating 'fs' as external dependency 
bundle update failed: Error transforming .../node_modules/typescript/lib/typescript.js
with 'commonjs' plugin: The keyword 'package' is reserved (57066:28) in
.../node_modules/typescript/lib/typescript.js

Surely I'm just missing something silly, even a typo. What can I do to use this code?

Answer 1

you have to import the type declarations together with the (js) library

npm install reflect-metadata -D

inside your .ts file:

 import "reflect-metadata";

Answer 2

As of today, @types/reflect-metadata is deprecated since reflect-metadata includes already its own typings.

So, to use them you just need to import the library (Uses the global scope). That's it.

1. Install it:
   npm install reflect-metadata --save

2. Import it:
   import 'reflect-metadata';