Angular and Typescript: Can't find names - Error: cannot find name

There is a work-around mentioned in the changelog for 2.0.0-beta.6 (2016-02-11) (listed under breaking changes):

If you use --target=es5, you will need to add a line somewhere in your application (for example, at the top of the .ts file where you call bootstrap):

///<reference path="node_modules/angular2/typings/browser.d.ts"/>

(Note that if your file is not in the same directory as node_modules, you'll need to add one or more ../ to the start of that path.)

make sure you have the correct reference path, i needed to add ../ to the start to get this working.

ES6 features like promises aren't defined when targeting ES5. There are other libraries, but core-js is the javascript library that the Angular team uses. It contains polyfills for ES6.

Angular 2 has changed a lot since this question was asked. Type declarations are much easier to use in Typescript 2.0.

npm install -g typescript

For ES6 features in Angular 2, you don't need Typings. Just use typescript 2.0 or higher and install @types/core-js with npm:

npm install --save-dev @types/core-js

Then, add the TypeRoots and Types attributes to your tsconfig.json:

{
  "compilerOptions": {
    "target": "es5",
    "module": "es6",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": false,
    "typeRoots": [
      "../node_modules/@types"
    ],
    "types" : [
      "core-js"
    ]
  },
  "exclude": [
    "node_modules"
  ]
}

This is much easier than using Typings, as explained in other answers. See Microsoft's blog post for more info: Typescript: The Future of Declaration Files

A known issue: https://github.com/angular/angular/issues/4902

Core reason: the .d.ts file implicitly included by TypeScript varies with the compile target, so one needs to have more ambient declarations when targeting es5 even if things are actually present in the runtimes (e.g. chrome). More on lib.d.ts