How to use ES6 modules from dev tools console

As far as I understand it, if I create an ES6 module, I can only import it from code that is itself a module. This means non-module code, i.e. inline Javascript, or the Chrome dev tools console can never access code that is in a module.

Is that true? Is there any way around this because it seems like a fairly extreme limitation.

Solution 1:

You can use dynamic import within Chrome's console.

import('path/to/module.js').then(m => module = m)

// [doSomething] is an exported function from [module.js].
module.doSomething()

Solution 2:

You can register the function or variable in the global namespace with a line like window.myFunction = myFunction or window.myVariable = myVariable. You can do this in the module where myFunction or myVariable are declared or do it in a separate module where they have been imported.

Once you've done this, you will be able to use myFunction and myVariable from the Chrome DevTools console.

For example:

import myModule from '/path/to/module.js';
window.myModule = myModule;

// in the console:
myModule.foo();

(Credit to @Evert for providing this solution in a comment, albeit in a rather roundabout way that took me a while to figure out.)

Solution 3:

There is a way to use the Chrome Dev Tools with ES6 modules, if you use VSCode and the Javascript Debugger for Chrome. I had some trouble to get it to work, but it was worth it. https://marketplace.visualstudio.com/items?itemName=msjsdiag.debugger-for-chrome

The VSCode debugger launches a new chrome window which is connected to the VSCode debugger. You can also use Chrome Dev Tools (F12) in this window as usual. It works with ES6 modules and you can set breakpoints, use the console, inspect variables, etc...

In case you have trouble to set up the debugger, this is how it worked for me:

• Go to the VSCode Debug Window (CTRL+SHIFT+D) -> select Add Configuration from dropdown -> Select Chrome Launch or Chrome Launch Legacy to change "launch.json"

my launch.json:

{
  "name": "Launch Chrome Legacy",
  "type": "chrome",
  "request": "launch",
  "url": "http://localhost:5000/auth/login",
  "webRoot": "${workspaceFolder}",
  "sourceMaps": true
},
{
  "name": "Launch Chrome",
  "request": "launch",
  "type": "pwa-chrome",
  "url": "http://localhost:5000/auth/login",
  "webRoot": "${workspaceFolder}",
  "sourceMaps": true
},

The key was to use "sourceMaps": true and "url": "http://localhost:5000/auth/login" instead of http://localhost:5000/blog", which is the page I actually want to debug. However, when the Debugger opens the new chrome window, my page was redirected to /auth/login, so I had to use this url.

• You can try to disable the Preview Version of the new debugger and use the Legacy version instead: Turn off Debug › JavaScript: Use Preview in the VSCode settings.
• Then Run Launch Chrome Legacy from the Debug Window in VSCode
• To set breakpoints in VSCode, open the javascript module from Loaded Scripts

Solution 4:

You can await a dynamic import within Chrome's console:

const Module = await import('./path/to/module.js')
Module.doSomething()

That dynamic import is roughly equivalent to:

import * as Module from './path/to/module.js';
Module.doSomething()

Solution 5:

You can call functions contained in Javascript modules from the Chrome developer console using import, as in @Kin's answer.

If you get error "TypeError: Failed to resolve module specifier", try using the full URL for the module file. For example, on Windows 10 with IIS running locally, and Chrome 87, this works for me:

// Call doSomething(), an exported function in module file mymodule.js
import('http://localhost/mysite/myfolder/mymodule.js').then((m) => { m.doSomething(); });