[node.js] How to NodeJS require inside TypeScript file?

How do I load a regular NodeJS module (from node_modules) from within a TypeScript class?

When I try to compile .ts file that contains:

var sampleModule = require('modulename');

Compiler prompts that I can't use require in this scope. (That line is at the beginning of the file).

The correct syntax is:

import sampleModule = require('modulename');

or

import * as sampleModule from 'modulename';

Then compile your TypeScript with --module commonjs.

If the package doesn't come with an index.d.ts file and its package.json doesn't have a "typings" property, tsc will bark that it doesn't know what 'modulename' refers to. For this purpose you need to find a .d.ts file for it on http://definitelytyped.org/, or write one yourself.

If you are writing code for Node.js you will also want the node.d.ts file from http://definitelytyped.org/.

Use typings to access node functions from TypeScript:

typings install env~node --global

If you don't have typings install it:

npm install typings --global

The best solution is to get a copy of Node's type definitions. This will solve all kinds of dependency issues, not only require(). This was previously done using packages like typings, but as Mike Chamberlain mentioned, Typings are deprecated. The modern way is doing it like this:

npm install --save-dev @types/node

Not only will it fix the compiler error, it will also add the definitions of the Node API to your IDE.