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JavaScript JavaScript Foundations Variables Null and Undefined

Null and Undefined video instructions are not relaying current functionality

I understand that code changes, but are there plans to update this video at some point? It was a bit frustrating, but learning experience, to hunt down why I wasn't seeing the same thing despite having the exact same code :P

Hi Israel,

What wasn't the same?

1 Answer

Jason Anello : well, when I ran this code in the console, it actually gave me two true results, even though the video says it would return true / false.

var myVar;

undefined = true;

console.log(typeof myVar === "undefined");
console.log(myVar === undefined);


Hi Jim,

According to this mdn page: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined as of ecmascript 5 the undefined property is no longer writable.

My best guess is that at the time of recording this video, Jim's browser was using an older version of the standard which did allow you to change the value of undefined Now it's no longer possible and so that line undefined = true is essentially ignored.