A bug of console.log() in IE11 under IE9 mode and below

Question

I found console.log() in IE11 under IE9 mode and below works wierd. If I create an empty object, then log it, it will show 'undefined', but by alerting it shows correctly. Is this happen to you guys, or just me?

var a ={};
a.b = false;
a.c = true;
console.log(a);  //undefined
console.log(a.b);  //undefined
console.log(a.c);  //true
alert(a); //[object Object]
alert(a.b); //false
alert(a.c); //true

Answer 1

I am not able to reproduce the issue using the F12 console in IE9 document mode.

Could you perhaps be looking at the return value instead of the printed message?

When you run the following code from the console:

var a = {}; console.log(a);

It will print the message in blue:

> [object Object] {}

And then display the return value to console.log in green:

undefined