bradshaw/electron-middle

Simple electron module to run middleware on file fetches

electron-middle

electron-middle is a way to add middleware behaviour to electron apps

To install, run npm install electron-middle

Example usage

This example will open a window that displays "Hello, world!"

// index.js
// Run this file with electron:
//   electron index.js
const middle = require('electron-middle')

// This is where the magic happens
middle.get((file, cb) => {
  if (file === "/index.html") {
    // Calling cb with a string or a buffer will behave as if a file was
    // found with that string or buffer as its contents
    cb("<p>Hello, world!</p>")
  } else {
    // Calling cb with no parameters will pass the buck to the next
    // middleware, and if there is none, the default file fetcher will
    // simply try to load a local file
    cb()
  }
})


function createWindow () {
  let win = new BrowserWindow({width: 800, height: 600})
  
  win.loadURL(url.format({
    pathname: 'index.html',
    protocol: 'file:',
    slashes: true
  }))
}

Usage

middle.get() takes a function with two arguments, file and cb.
file is the path to the file that electron is trying to access. (As you can see in the example above, the file doesn't need to actually exist).
cb is a function you must call exactly once, call it with a string or a Buffer if successful, or empty to let the next, or default handler deal with the request.

Example implementation

Here is the main code for electron-middle-pug, a middleware to compile .pug files to .html

// electron-middle-pug: index.js
const middle = require('electron-middle')
const pug = require('pug')
const fs = require('fs')
const path = require('path')

middle.get((file, cb) => {
  let ext = path.extname(file);
  if (ext == '.html') {
    let pugfile = file.replace('.html', '.pug')
    fs.access(pugfile, err => {
      if (err) {
        cb()
      } else {
        compilePug(pugfile, cb)
      }
    })
  } else {
    cb()
  }
})

function compilePug(pugfile, cb) {
  fs.readFile(pugfile, (err, data) => {
    if (err) {
      cb()
    } else {
      let fn = pug.compile(data.toString(), {})
      let html = fn({})
      cb(html)
    }
  })
}