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Why is this simple code from JavaScript incorrectly variable hoisting?

I'm trying to understand JavaScript variable hoisting and I'm getting confused with the documentation specified by Mozilla.

The documentation which I am referring to is here:

console.log(x === undefined); // true
var x = 3;

I am using the developer's console on Google Chrome to test this code which is on the latest version. When I execute the above code, I get returned false when the Mozilla documentation states that it should be returned true.

code example

This output above means that x is definitely being set to 3 before console.log() is run. Is this documentation specified by Mozilla incorrect or is there something I'm not understanding here?

Solution

  • It will return true the first time you run it, because x starts out as undefined. After you run
    var x = 3, x gets set to 3, so the next time you run the console.log(x === undefined) comparison it returns false, as x is no longer undefined.