Export declaration file for JavaScript function in TypeScript

Question

I'm new to TypeScript and I want to know how to write declaration file for custom JavaScript function. I tried this, but it give me error "Could not find a declaration file for module './main'." and don't give any IntelliSense in index.ts file.

main.js

var maths={ sum:function (a,b){ console.log(a+b)}}

module.exports=maths;

index.ts

import * as mt from "./main"
mt.sum(2,5);

type.d.ts

 declare module 'main' {
export function sum(a:number,b:number):void }

`

artem · Accepted Answer · 2018-05-17 14:18:26Z

1

This import

import * as mt from "./main"

is looking for either main.ts or main.d.ts in the same directory as index.ts.

So one thing you can try is to rename type.d.ts to main.d.ts and remove declare module 'main' from it, leave just export function sum at the top level. When imported that way, module name is taken from the file name. Also, you might have to remove reference to type.d.ts from your project (or tsconfig.json) if you have one.

ALternatively, you can try to change the import to

import * as mt from "main"

so that imported module name matches exactly the name given in declare module.

answered May 17, 2018 at 14:18

artem

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2 Comments

Chnkz Over a year ago

Appreciate the answer and it works.One more thing need to ask should be both d.ts file and .js file in same folder ?

artem Over a year ago

for import from "./main", main.js file should be in the same folder where compiled index.js is.

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