Global Scope and functions

1

I am doing FCC’s quiz #169, and here is something I don’t understand.

Let’s just say that I have these two variables.

var thisVar = 10;

function thisFunction( ){ thatVar=5; }

If any variables that does not have a var in front of it is a global variable, then what about thatVar? It was declared inside a function , but without the proper var in front of it. Is it a global variable or a local one?

2

It depends.
If you try to call thatVar without calling thisFunction beforehand, it’s an error. If you do call thisFunction it’ll create a global variable thatVar.

You should generally use ‘strict mode’, so this kind of code will throw error.

3

Strict mode means no matter what add the var ahead of any variables you declare?

4

Strict mode means you can’t use variable without declaring it.

https://docs.microsoft.com/en-us/scripting/javascript/advanced/strict-mode-javascript

And it’s 2017, use const and let

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