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:tophat: local Node/Browser development with Chrome DevTools

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Statistics on hihat

Number of watchers on Github 453
Number of open issues 14
Average time to close an issue 17 days
Main language JavaScript
Average time to merge a PR 25 days
Open pull requests 0+
Closed pull requests 0+
Last commit over 3 years ago
Repo Created about 4 years ago
Repo Last Updated over 1 year ago
Size 115 KB
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local Node/Browser development with Chrome DevTools

Runs a source file in a Chrome DevTools process. Saving the file will reload the tab.

This is useful for locally unit testing browser code with the full range of Web APIs (WebGL, WebAudio, etc). It provides access to profiling, debugger statements, network requests, and so forth.

It can also be used to develop typical Node projects, or as a generic Node REPL. For example, instead of using nodemon during development, you can use hihat to make use of a debugger.

Since it provides Browser and Node APIs, it can also be used for some simple CLI tooling, like saving a Canvas2D to a PNG file.

Under the hood, this uses electron, browserify and watchify.

Update: Jan 2016

A lot of new efforts are going toward devtool, a very similar project but without browserify and watchify under the hood. In many ways it replaces hihat, but not all. Both tools will continue to exist, although devtool will probably receive more regular enhancements and maintenance.



This project is currently best suited as a global install. Use npm to install it like so:

npm install hihat -g

Basic Examples

Simplest case is just to run hihat on any source file that can be browserified (Node/CommonJS).

hihat index.js

Any options after -- will be passed to browserify. For example:

# transpile ES6 files
hihat tests/*.js -- --transform babelify

You can use --print to redirect console logging into your terminal:

hihat test.js --print | tap-spec

The process will stay open until you call window.close() from the client code. Also see the --quit and --timeout options in Usage.



hihat [entries] [options] -- [browserifyOptions]


  • --port (default 9541)
    • the port to host the local server on
  • --host (default 'localhost')
    • the host for the local development server
  • --dir (default process.cwd())
    • the root directory to serve static files from
  • --print
    • console.log and console.error will print to process.stdout and process.stderr
  • --quit
    • uncaught errors (like syntax) will cause the application to exit (useful for unit testing)
  • --frame (default '0,0,0,0')
    • a comma-separated string for x,y,width,height window bounds
    • if only two numbers are passed, treated as width,height
    • if true is passed, uses the native default size
  • --no-devtool
    • do not open a DevTools window when running
  • --raw-output
    • do not silence Chromium debug logs on stdout/stderr
  • --node
    • enables Node integration (see node)
  • --no-electron-builtins
    • when --node is enabled, makes it behave more like Node by ignoring Electron builtins
  • --timeout (default 0)
    • a number, will close the process after this duration. Use 0 for no timeout
  • --exec
    • an alias for --print, --no-devtool and --quit options. Useful for headless executions
  • --index=path/to/index.html
    • optional index.html file to override the default (see HTML index)
  • --serve
    • what to serve your bundle entry point as
    • defaults to file name if possible, otherwise 'bundle.js'
  • --browser-field
    • Can specify true or false to force enable/disable the "browser" field resolution, independently of the --node option

By default, browserify will use source maps. You can change this with --no-debug as a browserify option:

hihat test.js -- --no-debug


Note: Users seeking the Node.js features may be more interested in devtool very similar to hihat but better architected to deal with large Node applications.

hihat can also be used for developing simple Node modules. The --node flag will disable the "browser" field resolution and use actual Node modules for process, Buffer, "os", etc. It also exposes require statement outside of the bundle, so you can use it in the Chrome Console while developing.

For example, foobar.js

var fs = require('fs')

fs.readdir(process.cwd(), function (err, files) {
  if (err) throw err

Now we can run the following on our file:

hihat foobar.js --node


By default, enabling --node will also enable the Electron builtins. You can pass --no-electron-builtins to disable Electron modules and make the source behave more like Node.


There are some known limitations with this approach.

  • Modules that use native addons (like node-canvas) are not supported.
  • Unlike a typical Node.js program, you will need to explicitly quit the application with window.close()
  • Since the source is run through browserify, the initial build time is slow and features like require.resolve are not yet supported. #21
  • Some features like process.stdin are not possible. #12
  • Since this runs Electron instead of a plain Node.js runtime, it may produce some unusual results


If you specify hihat without any entry files, it will not invoke browserify or watchify. For example, you can use this as a generic alternative to the Node REPL, but with better debugging and various Web APIs.

hihat --node



HTML index

By default, hihat will serve a simple HTML index.html file. You can use --index for an alternative. The path is relative to your current working directory.

hihat test.js --index=foo.html

And the following foo.html:

<!doctype html>
  <meta charset="utf-8">
  <script src="test.js"></script> 

You can also specify a --serve option to force a certain entry point for your bundle. For example:

hihat test.js --index=foo.html --serve=bundle.js

With this, your script tag would be:

<script src="bundle.js"></script> 

In most cases, --serve will default to the file name of your entry file. In complex cases, such as absolute paths or '.', it may default to 'bundle.js'.

Advanced Examples

Some more advanced uses of hihat.

prettify TAP in console

You can use the browserify plugin tap-dev-tool to pretty-print TAP output in the console.

# install it locally
npm install tap-dev-tool --save-dev

# now run it as a plugin
hihat test.js -- -p tap-dev-tool

Files that use tap or tape will be logged like so:


write clipboard to stdout

Using the clipboard module in Electron, we can write it to stdout like so.


var clipboard = require('clipboard')
process.stdout.write(clipboard.readText() + '\n')

Then run:

hihat paste.js --node --exec > clipboard.txt

This will write the clipboard contents to a new file, clipboard.txt.

save Canvas 2D to PNG image

Here is an example which writes a Canvas2D element into a new PNG image, using electron-canvas-to-buffer.


var toBuffer = require('electron-canvas-to-buffer')

var canvas = document.createElement('canvas')
var context = canvas.getContext('2d')
var width = canvas.width
var height = canvas.height

var gradient = context.createLinearGradient(0, 0, width, 0)
gradient.addColorStop(0, '#f39821')
gradient.addColorStop(1, '#f321b0')

context.fillStyle = gradient
context.fillRect(0, 0, width, height)

process.stdout.write(toBuffer(canvas, 'image/png'))

Now run the following:

hihat render.js --node --exec > image.png

And the result of image.png will be:


See Also

  • devtool - a similar tool, but built specifically for Node and without the browserify/watchify cruft


MIT, see for details.

hihat open issues Ask a question     (View All Issues)
  • over 3 years Running on Travis
  • almost 4 years Pipe results back to terminal
  • almost 4 years line numbers not maching
  • almost 4 years Shim process.exit
  • almost 4 years Question: lock electron version?
  • almost 4 years execute tasks on over "mainWindow.reload()"
  • almost 4 years require.resolve & improved Node compatibility
  • almost 4 years Quit after closing DevTools
  • almost 4 years source map on first run
  • almost 4 years source maps in entry file
  • almost 4 years Packaging / Communication with Server
  • almost 4 years unit testing
  • almost 4 years process.stdin
  • about 4 years general TODOs
hihat questions on Stackoverflow (View All Questions)
  • HIhat honeypot how to initiate the analysis tool
hihat list of languages used
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