About: Teaching you to code at js.coderslang.com - JavaScript, HTML, CSS, Node.js, React.js, React Native
What's the output?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
In JavaScript, the typeof operator always returns a string.
So, even though typeof undefined evaluates to undefined, it’s a string and not the primitive undefined value.
The string ’undefined’ is not equal to the value undefined.
ANSWER: the message false will appear in the console.
So, typeof always returns a string and if we do a check like
typeof undefined === undefined
it is actually checking whether the string undefined equal to the type undefined which is a false.
Instead if we do
typeof undefined === "undefined"
we will get true as we are comparing with the string "undefined" and with the result which is a string we get from typeof undefined.
If
typeof(undefined) == undefined, that'd meanundefinedhas no type, so it makes sense for the string"undefined"to be returned instead :D