Struggling with generating a TypeScript declaration file

Question

Struggling with generating a TypeScript declaration file

Struggling with creating a typescript definition file for a seemingly 'simple' npm module.

Here are the key points:

Problem: encounter an error when compiling TypeScript:

play.ts(1,9): error TS2305: Module '"/to/the/dir/node_modules/geojson/geojson"' has no exported member 'GeoJSON'.

Module: geojson (https://www.npmjs.com/package/geojson). The package consists of only one public function located in geojson.js:

  (function(GeoJSON) {
  GeoJSON.version = '0.3.0';
  GeoJSON.defaults = {};

  // The sole public function.
  // Converts an array of objects into a GeoJSON feature collection
  GeoJSON.parse = function(objects, params, callback) {
    ...
    ...
    ...
  (typeof module == 'object' ? module.exports : window.GeoJSON = {}));

The package.json contains

"main": "./geojson",
"name": "geojson",
//// I ADDED THIS TYPE DEF FILE
"typings": "./geojson.d.ts",

Based on this information

module name: geojson
parse: signature is parse(objects: any, params: any, callback?: any): any;
Is GeoJSON an interface?

The definition file named geojson.d.ts looks like this:

export declare module geojson {
    interface GeoJSON {
        parse(objects: any, params: any, callback?: any): any;
    }  
}

The tsconfig file appears as follows:

{
    "compilerOptions": {
     "target": "es5",
     "module": "system",
     "moduleResolution": "node",
     "sourceMap": true,
     "emitDecoratorMetadata": true,
     "experimentalDecorators": true,
     "removeComments": false,
     "noImplicitAny": false
    }
}

Attempting to import (tried numerous methods..) including:

import GeoJSON from 'geojson';
import geojson from 'geojson';
import {geojson} from geojson;
import geojson = require('geojson');
import GeoJSON = require('geojson');

Where am I going wrong?

typescript angular

Answer 1

Answer №1

If there are no available typings publicly, you should use the correct type declaration as shown below.

Instead of editing the package.json, consider either using the typings tool to consume typings or saving the type definition below in your source folder as something-or-other.d.ts. Also, remember to add exclude: [ "node_modules" ] to your tsconfig.json to avoid processing anything in the node_modules folder (as it currently processes everything recursively).

The module itself doesn't have a specific namespace or interface. However, keep in mind that within the file, there is a "namespace" (which may be confusing if you're used to .NET/Java, etc.)

declare module 'geojson' {
    export var version : string;
    export var defaults: Object;
    export function parse(data: Object, propreties: Object, callback?: Function) : Object;
}

To use it:

import * as geoJson from 'geojson';

var data = [
        { name: 'Location A', category: 'Store', lat: 39.984, lng: -75.343, street: 'Market' },
        { name: 'Location B', category: 'House', lat: 39.284, lng: -75.833, street: 'Broad' },
        { name: 'Location C', category: 'Office', lat: 39.123, lng: -74.534, street: 'South' }
      ];

var result = geoJson.parse(data, {Point: ['lat', 'lng']});
console.log(result);

This JavaScript code is generated:

"use strict";
var geoJson = require('geojson');
var data = [
    { name: 'Location A', category: 'Store', lat: 39.984, lng: -75.343, street: 'Market' },
    { name: 'Location B', category: 'House', lat: 39.284, lng: -75.833, street: 'Broad' },
    { name: 'Location C', category: 'Office', lat: 39.123, lng: -74.534, street: 'South' }
];
var result = geoJson.parse(data, { Point: ['lat', 'lng'] });
console.log(result);

Output:

c:\code\tmp\geojson>node build\main.js
{ type: 'FeatureCollection',
  features:
   [ { type: 'Feature', geometry: [Object], properties: [Object] },
     { type: 'Feature', geometry: [Object], properties: [Object] },
     { type: 'Feature', geometry: [Object], properties: [Object] } ] }

For more information on typings discovery, check out this blog post:

This is an "ambient" type declaration indicating the existence of a module called geojson with certain members. In your case, the module will be an NPM one located in node_modules.

There are different ways to write typings depending on whether you're working with a local JavaScript file or an npm package. For example, writing an "external" module type declaration involves providing a file name (module.d.ts for module.js) in the same directory. In such cases, the declaration does not include a "declare module" because it is directly tied to the .js file.

Answer 2

If there are no available typings publicly, you should use the correct type declaration as shown below.

Instead of editing the package.json, consider either using the typings tool to consume typings or saving the type definition below in your source folder as something-or-other.d.ts. Also, remember to add exclude: [ "node_modules" ] to your tsconfig.json to avoid processing anything in the node_modules folder (as it currently processes everything recursively).

The module itself doesn't have a specific namespace or interface. However, keep in mind that within the file, there is a "namespace" (which may be confusing if you're used to .NET/Java, etc.)

declare module 'geojson' {
    export var version : string;
    export var defaults: Object;
    export function parse(data: Object, propreties: Object, callback?: Function) : Object;
}

To use it:

import * as geoJson from 'geojson';

var data = [
        { name: 'Location A', category: 'Store', lat: 39.984, lng: -75.343, street: 'Market' },
        { name: 'Location B', category: 'House', lat: 39.284, lng: -75.833, street: 'Broad' },
        { name: 'Location C', category: 'Office', lat: 39.123, lng: -74.534, street: 'South' }
      ];

var result = geoJson.parse(data, {Point: ['lat', 'lng']});
console.log(result);

This JavaScript code is generated:

"use strict";
var geoJson = require('geojson');
var data = [
    { name: 'Location A', category: 'Store', lat: 39.984, lng: -75.343, street: 'Market' },
    { name: 'Location B', category: 'House', lat: 39.284, lng: -75.833, street: 'Broad' },
    { name: 'Location C', category: 'Office', lat: 39.123, lng: -74.534, street: 'South' }
];
var result = geoJson.parse(data, { Point: ['lat', 'lng'] });
console.log(result);

Output:

c:\code\tmp\geojson>node build\main.js
{ type: 'FeatureCollection',
  features:
   [ { type: 'Feature', geometry: [Object], properties: [Object] },
     { type: 'Feature', geometry: [Object], properties: [Object] },
     { type: 'Feature', geometry: [Object], properties: [Object] } ] }

For more information on typings discovery, check out this blog post:

This is an "ambient" type declaration indicating the existence of a module called geojson with certain members. In your case, the module will be an NPM one located in node_modules.

There are different ways to write typings depending on whether you're working with a local JavaScript file or an npm package. For example, writing an "external" module type declaration involves providing a file name (module.d.ts for module.js) in the same directory. In such cases, the declaration does not include a "declare module" because it is directly tied to the .js file.

Answer 3

Answer №2

It seems that the module definition you have written is not being exported properly, meaning it's not available publicly.

   declare module 'geojson' {
        export interface GeoJSON {
            parse(objects: any, params: any, callback?: any): any;
        }
   }

After fixing this issue, you should be able to use it like this:

import {GeoJSON} from 'geojson';

~~Have you checked if there are typings available for this library on DefinitelyTyped?~~ EDIT: Paul mentioned in the comments that the only typings available are for the GeoJson schema, not the entire library.

Answer 4

It seems that the module definition you have written is not being exported properly, meaning it's not available publicly.

   declare module 'geojson' {
        export interface GeoJSON {
            parse(objects: any, params: any, callback?: any): any;
        }
   }

After fixing this issue, you should be able to use it like this:

import {GeoJSON} from 'geojson';

~~Have you checked if there are typings available for this library on DefinitelyTyped?~~ EDIT: Paul mentioned in the comments that the only typings available are for the GeoJson schema, not the entire library.

Struggling with generating a TypeScript declaration file

Answer №1

Answer №2

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