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JavaScript

Posted by Alex Ng
Alex Ng
11,245 Points

Why did I not get an error when I forgot to declare each variable?

I didn't exactly write a ad-lib style story, but I got the idea.

However, for some reason I forgot to declare any of the variables, but did not get an errors from Chrome Dev Tools' JavaScript console. Why is that?

below is the entirety of what I wrote:

console.log ("Your Script started");

yourName = prompt("What's your Name?");

console.log ("Yes prompt 1");

yourAdjective = prompt("Pick an Adjective");

yourSentence = "Hey, " + yourName + ". You've got an "+ yourAdjective +" name. Jerk.";

document.write (yourSentence);

console.log ("Your Script Ended");

This was part of the Variable Challenge in JavaScript Basics.

Alex Ng
Alex Ng
11,245 Points

I should mention the output in the preview performed exactly as expected.

Alex Ng
Alex Ng
11,245 Points

Thanks, Elise!

1 Answer

Elise Kain
Elise Kain
54,392 Points
Elise Kain
Elise Kain
54,392 Points

Hi Alexander - When you forget the "var", "let" or "const" keyword to declare variables, they are still created but are automatically put in the "global" scope (so they are accessible anywhere). This is not a best practice, so it should be avoided whenever possible. However, since it "works", the Chrome Dev Tools did not give you an error.

See https://www.w3.org/wiki/JavaScript_best_practices#Avoid_globals and https://gist.github.com/hallettj/64478 for some more detail.