fake-api.js

/**
 * @typedef {(input: RequestInfo, init: RequestInit) => Promise<Response>} Request
 * @typedef {{ method: string, path: string, handler: Request, description?: string }} FakeRequest
 */

/**
 * @type {FakeRequest[]}
 */
export const REQUESTS = [
  {
    method: 'GET',
    path: '/api/user',
    handler: (input, options) => Promise.resolve({
      status: 200,
      ok: true,
      json: () => Promise.resolve([])
    })
  }
]

/**
 * simulate requests from remote api
 *
 * @param {FakeRequest[]} requests
 */
export function configure (requests = []) {
  const realFetch = window.fetch

  /**
   * override native fetch
   *
   * @param {RequestInfo} url
   * @param {RequestInit} [opts]
   * @returns {Promise<Response>}
   */
  window.fetch = (url, opts = { method: 'GET' }) => {
    /**
     * mock request
     */
    const fake = requests.find(value =>
      value.method.toUpperCase() === opts.method.toUpperCase() &&
      url.startsWith(value.path)
    )

    if (!fake) {
      return realFetch(url, opts)
    }

    if ('description' in fake) {
      console.log(`> [${fake.method}] ${fake.path}: ${fake.description}`)
    }

    return fake.handler(url, opts)
  }
}