How does the typeof method works in Javascript?
This question already has an answer here:
The first case is equivalent. The === performs the same operation as the == , except that it does not perform any type conversions . See this answer for more details.
So,
if ( variable === true || variable === false) {
...
}
Will evaluate to true only when variable is a boolean variable.
As for the inner workings of typeof , you can read this and, of course, it's manual. Keep in mind that typeof is a language operator, much like === , == , or & . To know exactly how it is implemented and how it knows the variable types, you need to check the code for it.
I never looked at a JavaScript Engine source code, so I don't know where you could look.
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