Cannot Determine is Variable is "undefined"

[gw1500se]

I an trying to determine if a cookie exists using the following code:

const json_str=Cookies.get("Auto_Select_051969");
if (!(json_str in window)) {
    create_cookie();
    json_str=Cookies.get("Auto_Select_051969");
}
json=JSON.parse(json_str);

When it gets to the parse I get the error:

Uncaught SyntaxError: "undefined" is not valid JSON
    at JSON.parse (<anonymous>)
    at cookie_mgmt.js:16:11

'create_cookie()' is not executed. If 'json_str' is undefined, per the error, how can it fail the 'if' test?

I also tried:

if (typeof(json_str)=="undefined") {

Which also fails the 'if' test.

Edited August 25, 2022 by gw1500se

[maxxd]

Have you tried swapping this:

!(json_str in window)

with this:

typeof json_str == "undefined"

 

[gw1500se]

Yes. With or without the parens, I get the same result.

[gw1500se]

I finally got it working but I can't explain how/why. I did:

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

The output was "true" which I expected. I then edited the line by changing 'console.log' to 'if' and changed the ';' to '{' and the thing started to work.

[maxxd]

Your last post isn't the same code as your first. It's the code I told you to run - the parenthesis have nothing to do with it, it's using typeof result as a comparator, not in window.

[gw1500se]

Except that didn't work either originally.