Inherited class from another module in Typescript -

i trying extend abstract class class, more convenience need have abstract class in file. unfortunately throws me runtime error struggle understand.

this works :

abstract class item{    constructor(){       console.log("i item");    } }  export class folder extends item{     constructor(){          super();     } } 

log :

i item 

this doesn't :

module mymodule{     export abstract class item{         constructor(){             console.log("i item");         }     } }  export class folder extends mymodule.item{     constructor(){         super();     } } 

compiles throws :

uncaught typeerror: cannot read property 'prototype' of undefined 

does understand going on ?

a top-level export (export class folder in case) in source file means typescript treat file external module, though unless specify module format when compiling typescript should have emitted error ts1148: cannot compile modules unless '--module' flag provided. so, i'm confused how managed compile code snippets @ if you're using internal modules.

i suggest using external modules (where each .ts file module in , of itself) , avoiding namespaces (previously known internal modules) entirely.

here's code nothing external modules:

// mymodule.ts export abstract class item {   constructor() {     console.log("i item");   } }  // folder.ts import * mymodule './mymodule';  export class folder extends mymodule.item {   constructor() {     super(); } 

however, if wanted stick using namespaces instead, you'd this:

namespace mymodule {   export abstract class item {     constructor() {       console.log("i item");     }   } }  namespace myothermodule {   export class folder extends mymodule.item {     constructor() {       super();     }   } }