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Google has an easter egg where if you search "text adventure" and then open the browser tools on the results page, you can start playing a text-based adventure game by entering words into the console:

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My question is, how does this work?

What could they be doing that allows their JavaScript to intercept browser console input and respond accordingly?

Other possibly relevant details:

  • Most console behavior appears to work like normal (defining variables, functions, debugger commands, etc.). It only behaves differently when a valid command is entered.
  • You can inspect the JavaScript that contains many of the strings and logic, but it's minified so it's hard to understand much of how it works.
  • It doesn't seem to be built into the browser, since the game works on Safari and Firefox.
  • They aren't just intercepting errors. If you define a variable that matches their keywords (like var yes = 'test';), and then enter yes they are still able to intercept the input.
bryanbraun
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  • `let yes = 'no'` should break it - but a global `var` doesn't change anything. – Bergi Apr 27 '20 at 21:42
  • @Bergi `Uncaught SyntaxError: Identifier 'yes' has already been declared`. @bryanbraun They are identifier and not text or string, I think that's how they catch it. They don't read your input you call their predefined identifier. If you type `"yes"` it just prints yes" – Mickael B. Apr 27 '20 at 21:45

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