Issue in the section 'Object to primitive conversion' under the 'toString/valueOf' here as well as in the summary section
It is implied that while converting Object to string the toString is called first if its not present then vallueOf is called, this is not correct, because if toString is not present javascript calls the Object.prototype's toString method which outputs "[Object Object]"
Here is Demo on JsBin https://jsbin.com/vikisihosa/edit?js,output