Electron handle console.log messages in main process

Question

Is there way to handle console.log messages from renderer in main process? Similar to CefDisplayHandler::OnConsoleMessage handler in Cef.

Answer 1

You can do this in three ways,

• Set the enviroment variableELECTRON_ENABLE_LOGGING=true to parse every console.log to your CLI
• Do a IPCrenderer message to IPCmain, which the logs it for you

• Add a function to app from the main process

  # MAIN
  const {app} = require('electron')
  app.MySuperCoolLoggingUtility = function (msg) { 
      console.log(msg) 
  }
  
  # RENDERER
  require('electron').remote.app.MySuperCoolLoggingUtility('hi')
  

There are also some ways to limit the log level for specific files via --vmodule= but it is not close to the handler of normal Cef. So you will probably build your own utility function for it.

Answer 2

The ability to intercept console messages generated by the renderer process, in the main process, was implemented in Electron version v1.8.2-beta.3 (as far as I were able to determine).

To be able to handle these messages, one attaches a "console-message" event handler to the webContents object property of a BrowserWindow object.

A rather straightforward replication of messages by the main process, could be implemented as follows (win refers to a BrowserWindow you want to capture messages for):

const log_level_names = { "-1": "DEBUG", "0": "INFO", "1": "WARN", "2": "ERROR" };
win.webContents.on("console-message", (ev, level, message, line, file) => {
    console.log(`${new Date().toUTCString()}\t${log_level_names[level]}\t${message} (${file}:${line})`);
});