Enda provides an interface for composing and formatting API endpoint URLs. It helps avoid potential typos by letting you maintain URL parts in a single place.

import { Enda } from 'enda';

const enda = new Enda({
  base: 'https://api.myapi.com',
  parts: {
    projects: 'projects',
    tasks: 'tasks',
    versions: {
      v1: 'v1',
      v2: 'v2'
    },
    params: {
      projectId: '{projectId}',
      taskId: '{taskId}'
    }
  }
});

const PROJECT_TASK = enda.make(({ join, parts }) =>
  join(
    parts.versions.v1,
    parts.projects,
    parts.params.projectId,
    parts.tasks,
    parts.params.taskId
  )
);

const getProjectTask = (projectId, taskId) => {
  const url = PROJECT_TASK.format({ projectId, taskId }); // e.g. https://api.myapi.com/projects/23/tasks/2
  return makeRequest(url);
};

Installation

Via npm:

npm install enda

Usage

new Enda([options])

• options: EndaOptions
  • base?: string Base URL - Default '/'
  • parts?: {[k: string]: string} URL parts
  • parameterMatcher?: RegExp Pattern used to match path parameters - Default /{([^}]+)}/g
  • strictParameterMatching?: boolean Whether an error will be thrown if a replacement for a path parameter matched by the parameterMatcher expression is not found when the format method is called - Default true

The base URL does not need to end with a / character. If not already present, this will be appended to base when joining paths.

Path parameters are matched based on the parameterMatcher Enda option. By default this is /{([^}]+)}/g. The method will use the matched contents of the first, outermost match group to look up a corresponding value in the path parameters object. If no match group is present, the full match will be used.

An error will be thrown if a match is found in the URL but no corresponding property is found in the path parameters object passed when formatting. You can disable this behavior by setting strictParameterMatching to false in the Enda options.

enda.make

Constructing an Enda object will give you access to a make method that can be used to create endpoint URLs based on the options provided.

make is an overloaded method and can take its arguments in a number of forms:

enda.make(): Endpoint

Calling make with no arguments will simply give you back an Endpoint instance whose underlying URL is the base URL.

import { Enda } from 'enda';

const enda = new Enda({ base: 'https://api.myapi.com' });

const base: Endpoint = enda.make();
base.url(); // https://api.myapi.com

enda.make(...parts: string[]): Endpoint

Calling make with any number of string arguments will give you back an Endpoint instance whose underlying URL is the base URL joined with the provided parts. Parts are joined using the / character, so there's no need to include this in each part string. enda will ignore any leading / characters.

import { Enda } from 'enda';

const enda = new Enda();

const project: Endpoint = enda.make('projects', '{projectId}');
project.url(); // /foo/bar/baz

// Leading / characters will be ignored...
const tasks: Endpoint = enda.make('projects', '/{projectId}', '//tasks');
tasks.url(); // /projects/{projectId}/tasks

enda.make(maker: MakerFunction): Endpoint

If a function is provided as the first argument to make it will be called with an object containing a join helper function and the parts provided when constructing the Enda instance. If no parts were provided, then parts will be undefined.

import { Enda } from 'enda';

const enda = new Enda({
  parts: {
    projects: 'projects',
    projectId: '{projectId}',
    tasks: 'tasks'
  }
});

const tasks: Endpoint = enda.make(({ join, parts }) =>
  join(parts.projects, parts.projectId, parts.tasks)
);
tasks.url(); // /foo/{projectId}/tasks

// You don't have to use the join helper function. As long as
// your function returns a string, you're set. You will need
// manually join using the / character though!
const task: Endpoint = enda.make(
  ({ parts: { projects, projectId, tasks } }) =>
    `${projects}/${projectId}/${tasks}/{taskId}`
);
task.url(); // /foo/{projectId}/tasks/{taskId}

Endpoint methods

The Endpoint instance returned from make provides two additional methods.

endpoint.url(): string

Get the endpoint URL as a string.

import { Enda } from 'enda';

const enda = new Enda({
  base: 'https://api.myapi.com'
});

const projects: Endpoint = enda.make('projects');

projects.url(); // https://api.myapi.com/projects

endpoint.format(pathParameters: PathParameters): string

• pathParameters: PathParameters Object mapping path parameters in the endpoint URL to their corresponding replacement values. Values can be either type string or number.

Format path parameters in the endpoint URL. The formatted URL will be returned as a string.

import { Enda } from 'enda';

const enda = new Enda({
  parts: {
    projects: 'projects',
    projectId: '{projectId}',
    tasks: 'tasks',
    taskId: '{taskId}'
  }
});

const task: Endpoint = enda.make(({ join, parts }) =>
  join(parts.projects, parts.projectId, parts.tasks, parts.taskId)
);

task.format({ projectId: 23, taskId: '2' }); // /projects/23/tasks/2