({} plus {}).length doesn’t understand?

  node.js, question

I didn’t understand this, it was printed at 30. What the hell? ? ?

According to the conversion rule of adding operators, if the operands are objects, their toString methods are called to convert them into strings and perform string connection operations.
{} converted to string"[object Object]"

({} plus {}).length


Log (("[objectobject]" plus "[object Object]").length);  //30