TSURL

Type safe URL construction and deconstruction

About

Until now you've probably been relying on keeping various bits of code in sync, or casting types as whatever you believe they should be to prevent errors when constructing, matching and or deconstructing URLs.

TSURL prevents the need for you to worry about keeping your path templates in sync with your URL parameters, worries about accidental // in paths, missing URL parameters, unintentional or missing trailing slashes, URL encoding and decoding, query parameter construction/deconstruction, and type casting.

Built on top of existing libraries that you're probably already using, such as path-to-regexp, encodeurl query-string, url-parse, etc, TSURL combines their functionality to provide a type safe interface for working with URLs and paths.

Browser support

This library only supports modern browsers (latest Chrome, Firefox, Safari, etc), due to a reliance on query-string@6 which only has support for modern browsers.

If you need to support older browsers (e.g. Internet Explorer) you should configure your bundler/compiler to compile both @jakesidsmith/tsurl and query-string.

Installation

npm i @jakesidsmith/tsurl -S

-S is shorthand for --save and will automatically add this to your package.json and package-lock.json where necessary.

Example with react-router

If you've ever used react-router this should be a great example of how TSURL can improve your code.

Let's define a TSURL for our user details page. This would be something like /users/id/ where id is the user's ID. react-router uses path-to-regexp behind the scenes and so would require a path with the syntax /users/:id/, but TSURL can handle this for you.

import { createTSURL, requiredString } from '@jakesidsmith/tsurl';

export const userDetailURL = createTSURL(['/users', requiredString('id')], {
  trailingSlash: true,
});

We can now use this TSURL instance to supply a path to our routes.

import UserDetailPage from './users';
import { userDetailURL } from './urls';

// ...

<Route path={userDetailURL.getPathTemplate()} component={UserDetailPage} />;

This outputs a path with the same syntax as required by react-router.

Now, if you wanted to navigate to this URL you'd probably previously have used string concatenation, a template string, or path-to-regexp to construct the path, but none of these offer type safety. Instead now you can use your TSURL instance to construct a path. It will enforce that you provide a string for the user's ID.

const whereWeWantToGo = userDetailURL.constructPath({ id: 'abc' }, {});

This will output /users/abc/ exactly as we'd expect, but would fail type checks if the id key was missing from the URL parameters object. The second argument is the query params object, but since we don't need any, we've just provided an empty object. Note: this method will throw an error if you somehow fail to supply the user id e.g. not using type checking, or cast your params to any.

What if we now needed to extract the current user ID from the URL? Well, we can handle that also.

try {
  const { id } = userDetailURL.deconstruct(window.location.href).urlParams;
  // Do something with the id
} catch (error) {
  // Bail here
}

It's sensible to wrap your deconstruct calls in a try/catch as if the URL doesn't match the schema previously provided, then this will throw an error. Unfortunately there's no way to check that the URL provided will match the schema at compile time.

Example with query params and type casting

Say we have a paginated users list, we may be storing the current page number in the query parameters. No worries, TSURL has got your back.

const userListURL = createTSURL(['/users'], {
  trailingSlash: true,
  queryParams: [optionalNumber('page')],
});

Here we've constructed a TSURL instance that will not only enforce that we provide a number (or nothing as we may not want to define the page number for the first page) when constructing a URL for this route, but also will give us sensible types for the parameters when deconstructing.

userListURL.constructPath({}, {}); // Is fine because page is optional
userListURL.constructPath({}, { page: 2 }); // Is fine because page should be a number

userListURL.constructPath({}, { page: '2' }); // Disallowed by types (would error)
userListURL.constructPath({}, { page: null }); // Disallowed by types (would error)

// The below deconstruct will handle casting the page query param to a number if found
userListURL.deconstruct(window.location.href);
// And output a type matching
interface Result {
  urlParams: {};
  queryParams: {
    page: number | undefined;
  };
}

Example with baseURL/basePath

If all of your requests are prefixed with a specific domain and or path you can provide a baseURL and or basePath as an option. The baseURL may include protocol, host, port, and base path, but I'd recommend using basePath for paths in most circumstances.

Note: the baseURL is not affected by the normalize option, except where a base URL with a trailing slash and a path with a leading slash would cause an unwanted double slash e.g. baseURL: https://domain.com/api/ and path /users would output https://domain.com/api/users instead of https://domain.com/api//users.

Example base URLs:

'domain.com'
'https://domain.com'
'http://localhost:1234'
'/api/'
'domain.com/api/'
'https://domain.com/api'
'http://localhost:1234/api'

Example output:

const url = createTSURL(['/users', requiredString('userId')], {
  baseURL: 'https://domain.com/',
  basePath: '/api',
});

url.getURLTemplate();
// https://domain.com/api/users/:userId
url.getPathTemplate();
// /api/users/:userId
url.constructURL({ userId: 'abc' }, {});
// https://domain.com/api/users/abc
url.constructPath({ userId: 'abc' }, {});
// /api/users/abc

Example using groups

If we have our API running on a different domain we can use groups to pre-fill baseURL, basePath (and or any other options) for client and API URLs.

const api = createTSURLGroup({
  baseUrl: 'https://server.com',
  basePath: '/api',
  trailingSlash: true,
});

const API_URLS = {
  users: api.createTSURL(['users']),
  user: api.createTSURL(['users', requiredString('userId')]),
  userImages: api.createTSURL(['users', requiredString('userId'), 'images']),
};

const client = createTSURLGroup({
  baseUrl: 'https://client.com',
  trailingSlash: false,
});

const CLIENT_URLS = {
  users: client.createTSURL(['users']),
  user: client.createTSURL(['users', requiredString('userId')]),
};

Example using splat

If we want to match any trailing part of a URL/path we can do so using a splat URL part.

const url = createTSURL(['user', requiredString('userId'), splat('splat')], {
  baseUrl: 'https://server.com',
  basePath: '/api',
  trailingSlash: false,
});

url.constructPath({ userId: 'abc' }, {});
// returns '/api/user/abc'

url.constructPath({ userId: 'abc', splat: ['posts', '123'] }, {});
// returns '/api/user/abc/posts/123'

url.deconstruct('https://server.com/api/user/abc');
// returns { urlParams: { userId: 'abc', splat: undefined }, queryParams: {} }

url.deconstruct('https://server.com/api/user/123/posts/123');
// returns { urlParams: { userId: '123', splat: ['posts', '123'] }, queryParams: {} }

Ignore sub-paths when you don't want to match a splat

In some cases you want your URL templates to match a specific template, but when deconstructing you don't mind if the URL/path contains additional sub-paths. In these cases you can pass the ignoreSubPaths option to the deconstruct method.

const url = createTSURL(['user', requiredString('userId')], {
  baseUrl: 'https://server.com',
  basePath: '/api',
  trailingSlash: false,
});

url.deconstruct('https://server.com/api/user/123/posts/123');
// throws an error

url.deconstruct('https://server.com/api/user/123/posts/123', {
  ignoreSubPaths: true,
});
// returns { urlParams: { userId: '123' }, queryParams: {} }

API

createTSURL

The createTSURL function, which is also the default export, will construct a TSURL instance.

This takes 1 or 2 arguments:

• URL schema - an array of strings and or parameters
• An options object (optional) - Options - see Options for more info

Returns TSURL with inferred keys for URL and query params.

createTSURLGroup

The createTSURLGroup function, returns an object with a createTSURL function.

This takes 1 argument:

• An options object - Options - see Options for more info

group.createTSURL

As with the named/default exported createTSURL, but inherits options from the group.

TSURL.getURLTemplate

Returns a path-to-regexp compatible URL (including the baseURL) string from your defined schema.

This method takes no arguments.

TSURL.getPathTemplate

Returns a path-to-regexp compatible path (excluding the baseURL) string from your defined schema.

This method takes no arguments.

TSURL.constructURL

Returns a string URL (including the baseURL).

This takes 2 arguments:

• The URL params for this URL - an object with keys that match the required/optional URL params
• The Query params for this URL - an object with keys that match the required/optional query params

Note: this method will throw an error if you have not supplied required url/query params somehow (e.g. if you are not using type checking because your app is written in JavaScript, or you have cast your params to any in TypeScript).

TSURL.constructPath

Returns a string path (excluding the baseURL).

This takes 2 arguments:

• The URL params for this URL - an object with keys that match the required/optional URL params
• The Query params for this URL - an object with keys that match the required/optional query params

Note: this method will throw an error if you have not supplied required url/query params somehow (e.g. if you are not using type checking because your app is written in JavaScript, or you have cast your params to any in TypeScript).

TSURL.constructQuery

Returns a string of query params (prefixed with ?) if any are provided.

This takes 1 argument:

• The Query params for this URL - an object with keys that match the required/optional query params

Note: this method will throw an error if you have not supplied required query params somehow (e.g. if you are not using type checking because your app is written in JavaScript, or you have cast your params to any in TypeScript).

TSURL.deconstruct

Returns the URL and query params extracted from a string URL/path.

This takes 1 or 2 arguments:

• URL/path - string - the URL you wish to extract parameters from
• An options object (optional) - Options - see Deconstruct Options for more info

Returns an object with urlParams and queryParams keys. Both of these keys will be objects containing the parameters you defined in your schema e.g.

interface Result {
  urlParams: {
    organization: string;
  };
  queryParams: {
    users: readonly string[];
    search: string;
    page: number | undefined;
  };
}

Note: this method will throw an error if the URL/path does not match the previously defined schema. You should always wrap calls to deconstruct in a try/catch as the string that you provide contains no type information, and we cannot check at compile time.

Options

The options object is the second argument to the createTSURL function. All available options are optional.

Options include:

• baseURL - string - base URL to prefix constructed URLs with (can include protocol, host, port, and base path e.g. https://domain.com/api).
• basePath - string | readonly string[] - path to prefix the schema (path parts) for all URLs created with the group.
• trailingSlash - boolean - enforce or remove trailing slashes. Does nothing by default.
• encode - boolean - whether to encode the URL when constructing. Defaults to true.
• decode - boolean - whether to decode the URL when deconstructing. Default to true.
• normalize - boolean - whether to strip all double slashes from the path (//, excluding the baseURL, except where this causes multiple trailing slashes e.g. createTSURL with baseURL: 'https://domain.com/api/' and path parts ['/users'] will construct https://domain.com/api/users). Defaults to true.
• queryArrayFormat - how to handle constructing/deconstructing query params that can have multiple values. This option is defined by the query-string package.
• queryArrayFormatSeparator - string - the separator to use when queryArrayFormat is set to separator. Defaults to ,.
• queryParams - an array of parameters.

Deconstruct Options

This is the second argument to the deconstruct function.

Options include:

• ignoreSubPaths - boolean - whether the deconstruction will allow sub-paths (stuff that appears after your defined template) in the provided URL/path
• ignoreInvalidEnums - boolean - whether the deconstruction will error or omit invalid values if the URL contains values for enum restricted fields that do not adhere to the enum (does not apply to requiredEnum fields)

Parameters

There are a lot of functions that you can use to define parameters.

The URL schema supports the following:

• requiredString
• requiredNumber
• requiredBoolean
• requiredEnum
• optionalString
• optionalNumber
• optionalBoolean
• optionalEnum
• splat

The query params schema supports the following:

• requiredString
• requiredNumber
• requiredBoolean
• requiredEnum
• optionalString
• optionalNumber
• optionalBoolean
• optionalEnum
• requiredStringArray
• requiredNumberArray
• requiredBooleanArray
• requiredEnumArray
• optionalStringArray
• optionalNumberArray
• optionalBooleanArray
• optionalEnumArray

Contributing

Setup

Ensure you are using a compatible version of NodeJS (16) and NPM (8).

If you're using NVM you can simply:

nvm use

And ensure you have NPM 8 installed globally:

npm i npm@8 -g

Then run a clean install to get fresh dependencies:

npm ci

Scripts

Run type-checking, linting and tests with:

npm test

You can fix formatting issues by running:

npm run prettier