How to NodeJS require inside TypeScript file?

Question

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).

Answer 1

Typescript will always complain when it is unable to find a symbol. The compiler comes together with a set of default definitions for window, document and such specified in a file called lib.d.ts. If I do a grep for require in this file I can find no definition of a function require. Hence, we have to tell the compiler ourselves that this function will exist at runtime using the declare syntax:

declare function require(name:string); var sampleModule = require('modulename'); 

On my system, this compiles just fine.

Answer 2

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/.