How to view JavaScript console on Android (and iOS)?

Just released for iOS, Chrome 73 now supports the option to see console.log.

If you’re a website developer, you can now view JavaScript console messages. Navigate to chrome://inspect to enable, then perform desired actions in another tab. Switch back to the same chrome://inspect tab to view any printed JavaScript console logs.

see here in "What's New" section or in "version history" 73.x version.

For Android you can use remote debugging through chrome as described here

I'll summarize/rewrite the steps (for browser based debugging) here in case the link ever goes down.

Requirements:

• For browser tabs: Android 4.0+ and Chrome for Android
• A USB cable to plug in your Android device
• Chrome 32 or later installed on your development machine

Set up:

• Enable USB debugging on your device.
• Navigate to chrome://inspect/#devices on your desktop Chrome browser. (Alternatively, to get to the same screen, you can select Chrome menu > Tools > Inspect Devices)
• After connecting, you may see an alert on the device requesting permission for USB debugging from your computer. Tap OK
• Chrome should now display the connected device
• Open up chrome on your Android device and navigate to the page you want to debug/inspect. The page should show up on your desktop browser and you should be able to inspect it.

If for some reason you have an older version of chrome and cannot upgrade. There is a plugin that you can install to accomplish the same thing.

Try https://github.com/liriliri/eruda

All you need to do is add this snippet on top of the page:

      <script src="//cdn.jsdelivr.net/npm/eruda"></script>
      <script>eruda.init();</script>