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pathy

A small library that will help you with interpolation of dynamic parameters in URLs or files paths as well as extracting them. Supports types validation and values casting.

Installation

yarn add pathy
# or
npm install --save pathy

API reference & usage

pathy([options: object]): object

import { applyParams, createRoute, extractParams } from "pathy";

const url = applyParams("/blog/posts/{postId:int}", { postId: 123 });
// url: "/blog/posts/123"

const route = createRoute("/blog/posts/{postId:int}");
// route: "/blog/posts/:postId(\\d+)"

const params = extractParams("/api/v1/{resource:str}/{postId:int}", "/api/v1/posts/123");
// params: { resource: "posts", postId: 123 }

And with custom types definitions (validation and casting):

import pathy from "pathy";

// Add some custom type validation and transformation.
const { applyParams, extractParams } = pathy({
  types: {
    customId: {
      parse: (value) => "id-" + value,
      regex: /(\d+)/,
    },
  },
});

const url = applyParams("/blog/posts/{id:customId}", { id: 123 });
// url: "/blog/posts/123"

const params = extractParams("/blog/posts/{id:customId}", "/blog/posts/123");
// params: { id: "id-123" }

Available options

{
  /**
   * (optional, default: false)
   *
   * Allow overwriting core types when 'types' option is specified (see below).
   * If this is not set or is set to false and you will provide a custom type with the same name
   * as built-in type, an error will be thrown.
   */
  overwriteTypes: boolean,

  /**
   * (optional, default: {})
   *
   * Extend library API with your own types.
   * This parameter accepts an object - each key in this object is a type name and the value can be:
   *  a) RegExp instance
   *  b) an object (use it only, if you want to specify 'parse' function):
   *      {
   *        // (required)
   *        // RegExp instance.
   *        regex: RegExp,
   *
   *        // (optional)
   *        // A function that will transform a raw parameter value to something else.
   *        parse: (string) => any
   *      }
   */
  types: {
    [string]: RegExp or { regex: RegExp } or { regex: RegExp, parse: (string) => any }
  }
}

applyParams(path: string, params: object): string

Replace parameters with values.

import { applyParams } from "pathy";

const url = applyParams("/blog/posts/{postId:int}", { postId: 123 });
// url: "/blog/posts/123"

const url = applyParams("http://someapi.com/api/v1/posts/{postId:int}", { postId: 123 });
// url: "http://someapi.com/api/v1/posts/123"

createRoute(path: string): string

Replace parameters with regular expressions and create a pattern you can use for matching routes, for example in express (compatible with path-to-regexp).

import { createRoute } from "pathy";

// For purpose of this example, let's agree that regular expression for integer is just (\d+).
// The built-in regexp for 'int' is way more strict.
const route = createRoute("/blog/posts/{postId:int}");
// route: "/blog/posts/:postId(\\d+)"

// You can make this method ignore names of the parameters in the output by providing 'false'
// as the second argument. Useful if you want to use 'createRoute' to make a RegExp instance:
// `new RegExp(createRoute(...))`
const route = createRoute("/blog/posts/{postId:int}", false);
// route: "/blog/posts/(\\d+)"

extractParams(path: string, url: string): object

Extract values for specified parameters. Each value can be mapped to some other type or value via parse method, so for example parameters annotated as int are transformed to number type.

import { extractParams } from "pathy";

const params = extractParams("/api/v1/{resource:str}/{postId:int}", "/api/v1/posts/123");
// params: { resource: "posts", postId: 123 }
// Notice, that postId is converted to a number.

// Params object will be empty, if at least one parameter cannot be matched.
const params = extractParams("/api/v1/{resource:str}/{postId:int}", "/api/v1/posts/not-an-integer");
// params: {}

Syntax

For defining dynamic parameter, the {name:type} syntax is used.

All parameters are forced to have a name.
My recommendation is to use camel-case naming convention, but anyway you are not limited as long as the parameter name matches /^[a-zA-Z0-9-_]+$/.

Each parameter must have also a type assigned to it. Type annotations are preceded by a colon (:) and are used for validating the value of the parameter.
This library provides a couple of most common types, but you can define your own. The core types are:

• bool (boolean values): true, false
• int (integer values): -100, 0, 123
• uint (non-negative integers): 0, 123
• float (numbers with decimals): -100.23, -100, 0.0, 1.0, 123.0
• uuid (strings in uuid format): a6715b7f-9f77-4166-bb55-f872735a22e6
• str (everything else): abc, two words, kebab-case

Typescript

Out-of-the-box Typescript support.

Live demo

You can see the live demo here. Don't hesitate to have some fun with it.

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Thank you!

A big shout-out to Richard Hoffman for letting me owning this package name ❤️