Debugging Typescript with Visual Studio Code

The problem involves using Typescript (as opposed to Javascript) as the language for a front-end program with the goal of debugging using the Visual Studio Code IDE’s debugger. The solution involves configuring Typescript compilation options, using a server to host the front-end program, using the Debugger for Chrome extension, and configuring Visual Studio Code launch options.

Motivation and context

I was resuming work on my game Kawaii Ketchup after a hiatus. An obstacle that appeared in my way, I had to solve the problem of being able to have debugging in Typescript using Visual Studio Code as I was previously using another IDE, NetBeans. So, with courage and skill I faced this problem and successfully found a solution.

My particular use case involves a browser-based program, a Phaser game, in fact, so the context for this informative guide will be that of a trying to get Visual Studio Code’s debugger to debug Typescript code that gets compiled to Javascript code which runs in a browser. The Chrome browser will be used as the browser for running the browser program.

Requirements

  • Visual Studio Code version 1.23.1
  • Microsoft Debugger for Chrome (with extension identifier msjsdiag.debugger-for-chrome) version 4.4.3
  • Live Server (with extension identifier ritwickdey.liveserver) version 4.0.0

Using a server

The Debugger for Chrome extension documentation says that a local web server must be used to serve the front-end program. I used the Visual Studio Code extension called Live Server. You could use the same or you could use something entirely different, like Python’s SimpleHTTPServer.

To use Live Server–and particularly for my use case of debugging a Phaser game–once the extension is installed, right-click the index.html file in the IDE’s explorer view pane and select “Open With Live Server” to have the index.html file served and the requirement for having a web server satisfied.

Typescript configuration

Create a mapping of Typescript source files to corresponding Javascript files. This will make the Visual Studio Code debugger be able to operate on your Typescript sources. Do this by enabling the sourceMap option in your tsconfig.json file.

{
    "compilerOptions": {
        "sourceMap": true
    },
}

Upon compilation, this will tell Typescript to create a .map file in the appropriate directory as configured in the tsconfig.json file.

To make Typescript automatically re-compile on file changes, use the following console command (in the appropriate directory)

tsc -w

Visual Studio Code launch options

Add a new debugging configuration in the Visual Studio Code IDE and allow the IDE to attach to Chrome with the “Chrome: Attach” debug configuration option.

After selecting “Attach to Chrome” as the debug launch configuration type, make your newly created launch.json file look a little something like this

{
    "type": "chrome",
    "request": "attach",
    "name": "Attach to Chrome",
    "port": 9222,
    "webRoot": "${workspaceFolder}",
    "sourceMaps": true
}

The line "sourceMaps": true is of concern as that will allow the .map files produced by Typescript compilations to be used by the Visual Studio Code IDE thereby allowing debugging. Depending on your project’s directory structure, additional configuration in the launch.json file may be required.

Begin debugging

The Visual Studio Code IDE needs to have an instance of the Chrome browser with remote debugging enabled. To accomplish this, run an instance of the Chrome browser with the launch options <PATH TO YOUR CHROME BROWSER'S BINARY FILE>/chrome.exe --remote-debugging-port=9222 as instructed by the Microsoft Debugger for Chrome extension [1]. Note that an instance of Chrome must not already be running. If one is, you’ll have to end that instance prior to launching an instance of Chrome with remote debugging enabled or else Visual Studio Code will not be able to debug your front-end program.

In Visual Studio Code, use the “Debug” menu or press the “F5” key, after which you’ll be prompted with a “Select a tab” drop-down menu that will allow you to select a Chrome tab as the debugging target. For instance, my use case involves me selecting the tab with the URL http://127.0.0.1:5500/public_html/index.html as the target.

You should now be able to debug your front-end program’s Typescript code using the Visual Studio Code IDE’s debugger.


Footnotes

Written on June 8, 2018