Typescript import/as vs import/require? [duplicate]

Question

These are mostly equivalent, but import * has some restrictions that import ... = require doesn't.

import * as creates an identifier that is a module object, emphasis on object. According to the ES6 spec, this object is never callable or newable - it only has properties. If you're trying to import a function or class, you should use

import express = require('express');

or (depending on your module loader)

import express from 'express';

Attempting to use import * as express and then invoking express() is always illegal according to the ES6 spec. In some runtime+transpilation environments this might happen to work anyway, but it might break at any point in the future without warning, which will make you sad.

import * as express from "express";

This is the suggested way of doing it because it is the standard for JavaScript (ES6/2015) since last year.

In any case, in your tsconfig.json file, you should target the module option to commonjs which is the format supported by nodejs.