About

Postman is a lightweight library that can download the assets of a web page asynchronously. A classic use-case might be a progress bar that is updated as assets are downloaded.

Example

Postman

Deliver

The "deliver" method initiates the download of a parcel that includes fonts, stylesheets and scripts. Each time an item is downloaded, the progress event is dispatched. When all items have been downloaded, the parcel is ready to be inserted into the DOM. Typically document.fonts is used to append fonts, document.head is used to append styles, and document.body is used to append scripts:

import { Postman, item } from "postman";

const items = [
  item.font("Roboto Regular", "/fonts/roboto-regular.ttf"),
  item.css("/css/main.css"),
  item.script("/js/main.js")
]

const postman = Postman(...items)
postman.addEventListener("progress", (event) => {
  const { progress, parcel } = event.detail
  console.info("progress", progress)
  if (progress === 100) {
    parcel.fonts.forEach((font) => document.fonts.add(font))
    parcel.css.forEach((style) => document.head.appendChild(style))
    parcel.scripts.forEach((script) => document.body.appendChild(script))
  }
})
postman.deliver()

Error

An "error" event is dispatched when an item fails to download, and that includes any item that was fetched with a response code other than 200. The dispatched event provides access to an instance of AbortController that can be used to cancel the download of the remaining items, otherwise the download will continue:

import { Postman, item } from "postman";

const items = [
  item.font("Roboto Regular", "/fonts/roboto-regular.ttf"),
  item.css("/css/main.css"),
  item.script("/js/main.js")
]

const postman = Postman(...items)
postman.addEventListener("error", (event) => {
  const { controller } = event.detail
  controller.abort()
  console.error("error encountered, download cancelled")
})
postman.deliver()

See also

• https://0x1eef.github.io/ Delivers assets with Postman
• https://al-quran.reflectslight.io/ Delivers all of its assets with Postman

Sources

• github.com/@0x1eef
• gitlab.com/@0x1eef
• brew.bsd.cafe/@0x1eef

License

BSD Zero Clause See LICENSE