There is something that I don't get in TypeScript when it comes to declaration files and third-party libraries written in pure Javascript. Let's say I have the following Javascript class:
$ cat SomeClass.js var SomeClass = (function () { function SomeClass() { } SomeClass.prototype.method1 = function () { return "some string"; }; return SomeClass; })(); exports.SomeClass = SomeClass;
And I want to get a type check for it, so I create a declaration file as follows:
$ cat test.d.ts class SomeClass { public method1(): string; }
Then I want to use the class and declaration file in some code:
$ cat main.ts ///<reference path="./test.d.ts"/> import ns = module("./SomeClass"); function test(): string { var sc = new ns.SomeClass(); return sc.method1(); }
When I try to compile it, I get the following:
$ tsc main.ts main.ts(2,19): The name '"./SomeClass"' does not exist in the current scope main.ts(2,19): A module cannot be aliased to a non-module type main.ts(5,16): Expected var, class, interface, or module
From what I can tell, the import statement requires the existence of an existing TypeScript class, and the reference statement is not enough to help the compiler figure out how to handle it.
I tried changing it to
import ns = module("./test.d");
But not the bones.
The only way I can do this to compile and run is to use the require statement instead of importing, for example:
$ cat main.ts ///<reference path="./node.d.ts"/> ///<reference path="./test.d.ts"/> var ns = require("./SomeClass"); function test(): string { var sc = new ns.SomeClass(); return sc.method1(); }
The problem with this code is that TypeScript does not perform type checking. In fact, I can completely delete the line
and doesn’t change anything.
However, if I delete the require statement, I can get a type check, but the code explodes at runtime because there is no require statement.
$ cat main.ts ///<reference path="./test.d.ts"/> function test(): string { var sc = new SomeClass(); return sc.method1(); } test(); $ node main.js main.js:2 var sc = new SomeClass(); ^ ReferenceError: SomeClass is not defined ...