teleman

Teleman

A tiny (~2kb after gzipped) fetch API wrapper.

Features

• Tiny, only about 2kb after gzipped.
• Supports middleware.
• Returns decoded response body by default.
• Handles response.ok for you.

Installation

npm i teleman

NOTE: The code is written in ES2020 syntax and not transpiled. To use it in old browsers, you should transpile the code using tools such as Babel.

Usage

import Teleman from 'teleman'

async function main() {
  const api = new Teleman({
    base: 'http://api.example.com'
  });

  const article = await api.get('/articles', { id: 123 });

  // post JSON
  await api.post('/articles', { title: 'Hello', content: '# Hello' });

  // post with Content-Type: multipart/form-data
  await api.post('/upload', new FormData(document.forms[0]));
}

Singleton

You can also use Teleman directly without creating an instance.

import { teleman } from 'teleman';

teleman.get(url, query, options);
teleman.post(url, body, options);
teleman.put(url, body, options);
teleman.patch(url, body, options);
teleman.delete(url, query, options);
teleman.head(url, query, options);
teleman.purge(url, query, options);
teleman.use(middleware);

Node.js

Node.js v18+ included native fetch.

Constructor

new Teleman({ base, headers, parseResponseBody = true, throwFailedResponse = true})

Creates a Teleman instance.

base

String. Optional. Base URL. In browser, it's default value is document.baseURI.

headers

Object. Optional. Default headers. It can be a simple key-value object or Headers object.

parseResponseBody

Boolean. Optional. Defaults to true. Whether to auto read the response body. According to content-type header of the response, it will use different methods:

• application/json: response.json()
• text/*: response.text()
• multipart/form-data: response.formData()
• Others: Won't read, manully handle the response in the middleware.

If you turn off parseResponseBody, you need to handle response body in the middleware.

const api = new Teleman({ parseResponseBody: false })

api.use(async(ctx, next) => {
  await next()
  return ctx.response.json()
})

throwFailedResponse

Boolean. Optional. Defaults to true. If response.ok is false, throw the response body.

Instance methods

teleman.fetch()

teleman.fetch(url, {
  method = 'GET',
  base = this.base,
  headers,
  query,
  params = {},
  body,
  parseResponseBody = this.parseResponseBody,
  throwFailedResponse = this.throwFailedResponse,
  use = this.middleware,
  useBefore = [],
  useAfter = [],
  ...rest } = {}
)

Parameters

url

String. The URL of the request. If it's a relative URL, it's relative to base parameter.

base

String. Base URL. The request URL will be new URL(url, base).

method

String. HTTP methods. GET, POST, PUT, PATCH, DELETE, HEAD, PURGE. Defaults to 'GET'.

headers

Object | Headers. HTTP headers. It will be merged with instance's default headers.

query

String | Object | Array | URLSearchParams. The query string appends to the URL. It takes the same format as URLSearchParams constructor's param.

params

Object. URL path params.

teleman.fetch('/articles/:id', { params: { id: 1 } })

It will use encodeURIComponent() to encode the values.

body

Object | FormData | Blob | BufferSource | URLSearchParams | String. The request body. If the body is a plain object, it will be converted to other type according to content-type of headers:

• not set: to JSON string, and set content-type to application/json.
• application/json: to JSON string.
• multipart/form-data: to FormData.
• application/x-www-form-urlencoded: to URLSearchParams.

parseResponseBody

Boolean. Whether to read response body.

throwFailedResponse

Boolean. Whether to throw when response.ok is false.

use

Array[function]. Middleware functions to use. Defaults to the middleware functions added by teleman.use().

useBefore

Array[function]. Applies middleware functions before use.

useAfter

Array[function]. Applies middleware functions after use.

...rest

Other params will be set into the context object.

Returns

teleman.fetch() returns a promise.

• If response.ok is true, the promise will be resolved with the response body, otherwise it will be rejected with the response body.
• If parseResponseBody is set to false, or content-type can't be handled, the promise will be resolved or rejected with no value, depending on response.ok. In this case, you should handle the response your self in the middleware.
• If any error occurs, the promise will be rejected with the error.

Shortcut methods

teleman.get(url, query, options)
teleman.post(url, body, options)
teleman.put(url, body, options)
teleman.patch(url, body, options)
teleman.delete(url, query, options)
teleman.head(url, query, options)
teleman.purge(url, query, options)

teleman.use(middleware, beginning = false)

Add the given middleware function to the instance.

Parameters

middleware

Function. The middleware function to use.

beginning

Boolean. Inserts the middleware function at the beginning of middleware chain. Defaults to false.

api.use(async(ctx, next) => {
  const start = Date.now()
  const data = await next()
  const ms = Date.now() - start
  console.log(`${ctx.options.method} ${ctx.url.href} - ${ms}ms`)
  return data
})

api.use(async(ctx, next) => {
  try {
    return await next()
  } catch (e) {
    alert(e ? e.message || e : 'fetch failed')
    throw e
  }
})

ctx

{
  url, // URL object
  options: { method, headers, body },
  response, // available after `await next()`
  parseResponseBody,
  ...rest
}

url and options are params of fetch():

fetch(ctx.url.href, ctx.options)

You can modify the context properties to interfere the request and response.

next

A middleware function should receive response body from next(), and can optionally transform the data. Finally it should return the data.

License

MIT

Big Thanks

Cross-browser Testing Platform and Open Source <3 Provided by Sauce Labs