CODEWITHSUNDEEP
typescripttypescript-typings
Loupax
Loupax

Reputation: 4914

Cannot invoke an expression whose type lacks a call signature, while it has a signature

I am trying to define types for a module I installed via npm.

This is the exported module. I'd rather not make changes to this file since I'd like to merge back to the original repo without introducing BCs

/**
 * Given a number, return a zero-filled string.
 * From http://stackoverflow.com/questions/1267283/
 * @param  {number} width
 * @param  {number} number
 * @return {string}
 */
module.exports = function zeroFill (width, number, pad) {
  if (number === undefined) {
    return function (number, pad) {
      return zeroFill(width, number, pad)
    }
  }
  if (pad === undefined) pad = '0'
  width -= number.toString().length
  if (width > 0) return new Array(width + (/\./.test(number) ? 2 : 1)).join(pad) + number
  return number + ''
}

This is the definition I wrote for this file

declare module "zero-fill"{
    export default function zeroFill(width:number, num:number, pad?:string|number):string;
    export default function zeroFill(width:number):{(num:number, pad?:string|number):string};
}

And here is an example usage:

import * as zeroFill from "zero-fill";
zeroFill(2,0);

What confuses me is that the compiler both gives me this error:

Cannot invoke an expression whose type lacks a call signature. Type 'typeof "zero-fill"' has no compatible call signatures.

while at the same time it compiles the typescript and I see it running in the browser. What seems to be the problem?

Upvotes: 0

Views: 1779

Answers (2)

Loupax
Loupax

Reputation: 4914

Here is what I ended up doing

Definition:

declare module "zero-fill" {
    function zeroFill(width:number, num:number, pad?:string|number):string
    function zeroFill(width:number):{(num:number, pad?:string|number):string}
    export  = zeroFill
}

Usage:

import zeroFill = require("zero-fill")
zeroFill(4, 1) // '0001'
zeroFill(10, 55) // '0000000055'
zeroFill(1, 1) // '1'

Upvotes: 2

y2bd
y2bd

Reputation: 6456

When you import * as zeroFill you're actually naming the module itself zeroFill. To call the function, you'd have to go zeroFill.zeroFill(2, 0), where the first zeroFill is the import alias and the second zeroFill is the function.

Upvotes: 0

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