Can I extend the console object (for rerouting the logging) in javascript?

Question

Is it possible to extend the console object?

I tried something like:

Console.prototype.log = function(msg){
    Console.prototype.log.call(msg);
             


        

Answer 1

For ECMAScript 2015 and later

You can use the newer Proxy feature from the ECMAScript 2015 standard to "hijack" the global console.log.

Source-Code

'use strict';

class Mocker {
  static mockConsoleLog() {
    Mocker.oldGlobalConsole = window.console;

    window.console = new Proxy(window.console, {
      get(target, property) {
        if (property === 'log') {
          return function(...parameters) {
            Mocker.consoleLogReturnValue = parameters.join(' ');
          }
        }

        return target[property];
      }
    });
  }

  static unmockConsoleLog() {
    window.console = Mocker.oldGlobalConsole;
  }
}

Mocker.mockConsoleLog();

console.log('hello'); // nothing happens here

Mocker.unmockConsoleLog();

if (Mocker.consoleLogReturnValue === 'hello') {
  console.log('Hello world!'); // Hello world!
  alert(Mocker.consoleLogReturnValue);
  // anything you want to do with the console log return value here...
}

Online Demo

Repl.it.

Node.js users...

... I do not forget you. You can take this source-code and replace window.console by gloabl.console to properly reference the console object (and of course, get rid of the alert call). In fact, I wrote this code initially and tested it on Node.js.