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Thank you. And thank you for making it open source. Concerning this line: https://github.com/arkadiyt/zoom-redirector/blob/master/background.js#L10 https://git

Thank you. And thank you for making it open source. Concerning this line: https://github.com/arkadiyt/zoom-redirector/blob/master/background.js#L10 https://github.com/arkadiyt/zoom-redirector/blob/master/back... Why is it sometimes returning undefined? (or is that known)? Cheers!

squeaky-clean 5y ago
Not the developer but nice catch. const match would be null, not undefined, if the regex search does not match, right?
- cipherboy 5y ago
  In a browser console: > const match = /^\/[js]\/(\d+)\/?$/.exec("something") > undefined
  - eatingCake 5y ago
    The assignment to match returns undefined. The value of match is null.
    - femto113 5y ago
      To be pedantic the assignment returns null (always returns the rvalue[1]), it's the const statement that produces undefined[2] [1] https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-let-and-const-declarations-runtime-semantics-evaluation https://tc39.es/ecma262/multipage/ecmascript-language-statem... [2] https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-let-and-const-declarations-runtime-semantics-evaluation https://tc39.es/ecma262/multipage/ecmascript-language-statem...
      - cipherboy 5y ago
        And to be even more pedantic, the function works because it is applied on an event listener... When null[1] is evaluated (in the right side of the || of the conditional), it produces a TypeError... which in effect (due to no catch and evaluation continuing in a parent/event-driven scope) is essentially equivalent to an empty return in this specific context. What fun! :-) Edit: apparently as also mentioned https://news.ycombinator.com/item?id=30268412 https://news.ycombinator.com/item?id=30268412
  - zeven7 5y ago
    Run just /^\/[js]\/(\d+)\/?$/.exec("something") in the console
vinayakpandey 5y ago
A function returns undefined if any value was not returned.
- chrismorgan 5y ago
  True generally, but irrelevant here: the function in question is RegExp.prototype.match. By definition, it never returns undefined, but only an array or null. The only way `match == undefined` could be true would be if smething had overridden RegExp.prototype.match, which would be… surprising and worthy of explicit note. Also match[1] will never be undefined: it’ll either throw an exception, or be a string. No, this is just a bug, a poorly written guard that fails to guard what it was supposed to, and I suppose an exception is just silently swallowed and treated equivalently to the intended early return. But the clause should be changed to just `if (!match) return;` or similar.
  - olliej 5y ago
    Quick heads up you may want to update that to be === rather than ==, because of course JS is wonderful and null does == undefined (not a nerd snipe, I was just confused by your comment and went and looked at the code, and realized it was likely a typo :) )
    - chrismorgan 5y ago
      Yeah, unfortunate typo, thanks for the correction. I spend most of my time writing Rust, and when I’m writing JavaScript I type !== and === naturally, but I think writing this comment I just didn’t quite switch into JavaScript mode.
arkadiyt 5y ago
> Thank you. And thank you for making it open source. Sure thing. All browser extension source code is available to you anyhow, even if the author doesn't publish it. > Why is it sometimes returning undefined? Looks like a simple bug as some folks below have pointed out. It doesn't impact the functionality of the extension in any way here.

squeaky-clean 5y ago

Not the developer but nice catch. const match would be null, not undefined, if the regex search does not match, right?

cipherboy 5y ago
In a browser console: > const match = /^\/[js]\/(\d+)\/?$/.exec("something") > undefined
- eatingCake 5y ago
  The assignment to match returns undefined. The value of match is null.
  - femto113 5y ago
    To be pedantic the assignment returns null (always returns the rvalue[1]), it's the const statement that produces undefined[2] [1] https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-let-and-const-declarations-runtime-semantics-evaluation https://tc39.es/ecma262/multipage/ecmascript-language-statem... [2] https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-let-and-const-declarations-runtime-semantics-evaluation https://tc39.es/ecma262/multipage/ecmascript-language-statem...
    - cipherboy 5y ago
      And to be even more pedantic, the function works because it is applied on an event listener... When null[1] is evaluated (in the right side of the || of the conditional), it produces a TypeError... which in effect (due to no catch and evaluation continuing in a parent/event-driven scope) is essentially equivalent to an empty return in this specific context. What fun! :-) Edit: apparently as also mentioned https://news.ycombinator.com/item?id=30268412 https://news.ycombinator.com/item?id=30268412
- zeven7 5y ago
  Run just /^\/[js]\/(\d+)\/?$/.exec("something") in the console

vinayakpandey 5y ago

A function returns undefined if any value was not returned.

chrismorgan 5y ago
True generally, but irrelevant here: the function in question is RegExp.prototype.match. By definition, it never returns undefined, but only an array or null. The only way `match == undefined` could be true would be if smething had overridden RegExp.prototype.match, which would be… surprising and worthy of explicit note. Also match[1] will never be undefined: it’ll either throw an exception, or be a string. No, this is just a bug, a poorly written guard that fails to guard what it was supposed to, and I suppose an exception is just silently swallowed and treated equivalently to the intended early return. But the clause should be changed to just `if (!match) return;` or similar.
- olliej 5y ago
  Quick heads up you may want to update that to be === rather than ==, because of course JS is wonderful and null does == undefined (not a nerd snipe, I was just confused by your comment and went and looked at the code, and realized it was likely a typo :) )
  - chrismorgan 5y ago
    Yeah, unfortunate typo, thanks for the correction. I spend most of my time writing Rust, and when I’m writing JavaScript I type !== and === naturally, but I think writing this comment I just didn’t quite switch into JavaScript mode.

arkadiyt 5y ago

> Thank you. And thank you for making it open source. Sure thing. All browser extension source code is available to you anyhow, even if the author doesn't publish it. > Why is it sometimes returning undefined? Looks like a simple bug as some folks below have pointed out. It doesn't impact the functionality of the extension in any way here.