Import vs Require in Typescript

Question

While I was going through Angular2 documentation, I came across below code in here.

src/polyfills.ts

import 'core-js/es6';
import 'core-js/es7/reflect';
require('zone.js/dist/zone');

if (process.env.ENV === 'production') {
 // Production
} else {
 // Development
Error['stackTraceLimit'] = Infinity;
require('zone.js/dist/long-stack-trace-zone');
}

In the above code we can see that there are both import and require statements.

"core-js" and "zone.js" are both node modules.

My question is; why is import used for core-js and require for "zone.js", is there any specific reason for this?

Answer 1

With TypeScript, import can be used if there is a declaration file (see Declaration Files in basarat's book) for the module.

If there isn't a declaration file, the TypeScript compiler doesn't know if the module exists, so you need to use require instead which lacks the compilation checking.