Why is custom toString in JS not being used for console.log?

In JavaScript I override toString on certain classes (using ES6 classes if it makes a difference), for example a subclass of an Error object. When I do console.log(myObject), my toString isn't getting called, it's instead using the default string output for that object.

It's not just console.log that isn't using my function, but other places where the object should be converted to a string.

I have to explicitly do console.log(myObject.toString()). Is this expected, or am I doing something wrong? I thought the purpose to toString was to serve as the default string output.

Otherwise is there any point in overriding toString? I could call my function customStringOutput for example and do console.log(myObject.customStringOutput()).

via user779159