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

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

API

createTSURL

The createTSURL function, which is 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.

TSURL.getURLTemplate

Returns a path-to-regexp compatible string from your defined schema.

This method takes no arguments.

TSURL.construct

Returns a string URL/path.

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 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 a single argument:

• URL/path - string - the URL you wish to extract parameters from

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:

• protocol - string | false - protocol to enforce, or remove if set to false. Does nothing by default.
• 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 (//, including those that may be part of a protocol). Defaults to true. You should define an explicit protocol to avoid // being stripped from the protocol if your URL contains one.
• 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.

Parameters

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

The URL schema supports the following:

• requiredString
• requiredNumber
• requiredBoolean
• optionalString
• optionalNumber
• optionalBoolean

In addition to the ones listed above, the query params schema also supports the following:

• requiredStringArray
• requiredNumberArray
• requiredBooleanArray
• optionalStringArray
• optionalNumberArray
• optionalBooleanArray