A mobile web app has a hidden “Send diagnostics” button. When a user taps it, support wants the recent console output attached to the bug report, without changing any of the app’s existing logging calls and without hiding the logs from the developer tools.

Implement recordConsole(methods). It starts recording calls to the given console methods and returns a recorder.

const recorder = recordConsole(methods = ['log']);

recorder.entries();  // => Array<{ method: string, args: unknown[] }>
recorder.clear();    // forget recorded calls, keep recording
recorder.restore();  // stop recording and put the original methods back

Recording

methods is an array of console method names, such as ['log', 'warn', 'error']. It defaults to ['log']. Names listed more than once are recorded once per call. Names that are not functions on console are ignored.
After recordConsole returns, calling one of those methods (for example console.warn('low disk', 12)) records an entry { method: 'warn', args: ['low disk', 12] }.
Every call is still forwarded to the method that was there before, with console as this and the same arguments. The wrapper returns whatever that method returns.
If the original method throws, the call is still recorded and the error propagates to the caller.
args is a new array holding the original argument values (objects are kept by reference, not copied).
Methods not in the list are not touched.

Recorder

entries() returns a new array of the recorded entries in call order, across all recorded methods. Changing the returned array does not affect the recorder.
clear() empties the history. Recording continues.
restore() puts back exactly the functions that were on console when recordConsole was called, and the recorder never records again. Calling it twice is safe. entries() still returns what was recorded.
Several recorders can be active at once. Each one records independently, so a call made while two recorders are active appears in both. Recorders are restored in reverse order of creation (the newest first).

Example

const recorder = recordConsole(['log', 'warn']);

console.log('boot', { build: 42 });  // still printed in the dev tools
console.warn('slow network');
console.info('not recorded');

recorder.entries();
// => [
//   { method: 'log', args: ['boot', { build: 42 }] },
//   { method: 'warn', args: ['slow network'] },
// ]

recorder.clear();
console.log('after clear');
recorder.entries(); // => [{ method: 'log', args: ['after clear'] }]

recorder.restore();
console.log('not recorded');
recorder.entries(); // => [{ method: 'log', args: ['after clear'] }]