Trying to understand why the first eval expression doesn't work, but the second does.

It is for a macro parser my values are "AM\" and "ABC".

eval('\"AM\\\"!=\"ABC\"');
> Error: Unexpected identifier

eval('\"AM\\\\"!=\"ABC\"');
> true

Can someone explain why you need four backslashes

console.log(eval('\"AM\\\\"')); 
> "AM\" 

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