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I never ever use try/catch in my code. The only time its really necessary is to wrap JSON.parse on use of untrusted input. For everything else it just feels sl

I never ever use try/catch in my code. The only time its really necessary is to wrap JSON.parse on use of untrusted input. For everything else it just feels sloppy as through there is insufficient logic in place for handling primary conditions versus edge cases. Also, try/catch will never compile in the JIT.

macguillicuddy 3y ago
Perhaps the place I use it most is that try/catch is how you deal with rejected promises that you've `await`ed in an `async` function.
raxxorraxor 3y ago
For everything with the slightest bit of I/O it is quite practical if you have even the most trivial assumptions about its form. Sure, you can check for everything. It often is more effective, but not prettier or easier to read and of course you also will miss cases.
- austin-cheney 3y ago
  This sounds like some hyperbolic framework nonsense. First of all I/O just means access to an API. I am going to presume you mean messages from a network. In that case a message from a network either sends or fails and in the case of sending try/catch does nothing for you but provide an error object, and you don't need try/catch to capture the error. In the case of receiving a network message the message comes in or it doesn't. If the message does come in and is malformed your application should be mature enough to handle that appropriately to the benefit of the user instead of crapping out some error messaging to the console. You don't need try/catch to do any of this. A simple if condition is more than sufficient. > check for everything You should check for everything. You only need to check for one thing and if you check for it you are already at 100% of everything. Did you get what you expected: Yes/No?
  - thrashh 3y ago
    Disagree. Usually you don't need to just know if there is an error or not -- sometimes you need to know what that error is. For example, an I/O error versus your image-is-too-small error -- you need to respond to the user differently. I've seen plenty of web apps that treat I/O errors and user input errors as a generic "an error happened" and that is completely wrong. Proper exception bubbling means none of that code that encounters the errors needs to necessarily know how to handle the error and your app always responds correctly. That said, I don't use exceptions as much in JS because exception handling in JS is still very nascent. There's no base library of exceptions and telling different exceptions apart is not built-in to the language. In a language with more mature exception handling, it's a breeze.
    - austin-cheney 3y ago
      You made the same mistake as the grandparent by assuming I/O means something more specific than it does. At any rate there isn't a good reason to bubble error objects out of the event handler and secondly even if you did you would have everything you need to fully describe the problem within the error object including the stack trace, event type, error message, and so forth. Its an equivalent breeze in JavaScript as well unless you are fumbling through abstraction layers (frameworks) that eliminate the information you need.
      - thrashh 3y ago
        Not at all. You don't have to describe anything when throwing an error because that's the point of exception inheritance. Second, the whole point of exceptions is to bubble them out of the handler(!) because otherwise you would use return values (like in Go). Since you are saying that you have to describe the problem within the error object, it sounds like you must be you are parsing error messages and stack traces to figure out what the error is. That's not how exceptions are to be used and I think that's why you are not seeing why you would bubble errors. In other languages, you don't have to do any of that nonsense because object identity is much stronger, but JavaScript uses prototypical inheritance so you can't really tell if an error is an ImageError or an IOError. Despite this issue, exceptions were added to the JavaScript language without resolving that problem. The reason why you have to worry about frameworks eliminating error information is because that problem wasn't resolved and so frameworks roll their own error handling and there is no standard.
afavour 3y ago
> Also, try/catch will never compile in the JIT Changing the way you program to fit what a JS compiler does or doesn't do is a fool's errand, IMO. The performance benefits are likely to be minimal, confusion for anyone else who has to touch the codebase is high.
- madeofpalk 3y ago
  And, JS engine's whims change frequently enough that yesterdays micro-optimisation is today's deopt. Much better to just write ideomatic code.
- austin-cheney 3y ago
  That depends on how many changes it requires. If its just a matter of don't do these 3 things and your code suddenly becomes more predictable its like being slapped with a magic wand. Everybody wins. All you have to do to ensure 100% of your code compiles in a JIT is be predictable. Predictable code is, on its face, always less confusing. > The performance benefits are likely to be minimal This makes me cry, but not a cry of joy or ecstasy. People guessing about performance is perhaps the most frequent anti-pattern in all programming. Please read the following document, you can skip to the end but it may not make much sense if you do. https://github.com/prettydiff/wisdom/blob/master/JavaScript_Made_Simple.md https://github.com/prettydiff/wisdom/blob/master/JavaScript_... When developers make random performance assumptions, defensive assumptions are worse, it immediately identifies a lack of professional maturity. Its like small children playing games that expand their imagination, which is great for small children but less great for developers pretending to be adults.
  - afavour 3y ago
    > People guessing about performance is perhaps the most frequent anti-pattern in all programming I disagree, premature optimisation is. Changing your style of programming to suit what todays JIT does but tomorrow’s may not, in anticipation of performance issues you have not yet encountered is a waste of everyone’s time. No doubt it is valuable in extremely performance sensitive code but that is the extreme minority, especially in the JavaScript world. If I were involved in a project where performance concerns were high enough to require everyone know what the JIT is and is not doing my proposal would be to use a language other than JavaScript. If thinking this makes me a “small child” in your mind I’m fine with that.
eyelidlessness 3y ago
> Also, try/catch will never compile in the JIT. If this is an actual concern (as in you have measured and try/catch is actually affecting something performance sensitive): you can most likely mitigate the impact by isolating the try/catch bodies in separate functions. I haven’t verified this in every JIT, but I saw meaningful perf improvement in V8 for real world degenerate cases where the performance did actually matter and make a significant difference. But seriously, as always, measure before optimizing stuff like this! It might matter, but it seldom will for anything more than academic curiosity.
magicalist 3y ago
> Also, try/catch will never compile in the JIT This was only ever true in V8, and hasn't been the case since 2017 with the optimizing compiler switch from Crankshaft to TurboFan. Take a break before lecturing commenters on "guessing about performance is perhaps the most frequent anti-pattern in all programming" next time :)
simlevesque 3y ago
> Also, try/catch will never compile in the JIT That's false. It used to be this way with Crankshaft but since 2017 we have Turbofan which solves this.

macguillicuddy 3y ago

Perhaps the place I use it most is that try/catch is how you deal with rejected promises that you've `await`ed in an `async` function.

raxxorraxor 3y ago

For everything with the slightest bit of I/O it is quite practical if you have even the most trivial assumptions about its form. Sure, you can check for everything. It often is more effective, but not prettier or easier to read and of course you also will miss cases.

austin-cheney 3y ago
This sounds like some hyperbolic framework nonsense. First of all I/O just means access to an API. I am going to presume you mean messages from a network. In that case a message from a network either sends or fails and in the case of sending try/catch does nothing for you but provide an error object, and you don't need try/catch to capture the error. In the case of receiving a network message the message comes in or it doesn't. If the message does come in and is malformed your application should be mature enough to handle that appropriately to the benefit of the user instead of crapping out some error messaging to the console. You don't need try/catch to do any of this. A simple if condition is more than sufficient. > check for everything You should check for everything. You only need to check for one thing and if you check for it you are already at 100% of everything. Did you get what you expected: Yes/No?
- thrashh 3y ago
  Disagree. Usually you don't need to just know if there is an error or not -- sometimes you need to know what that error is. For example, an I/O error versus your image-is-too-small error -- you need to respond to the user differently. I've seen plenty of web apps that treat I/O errors and user input errors as a generic "an error happened" and that is completely wrong. Proper exception bubbling means none of that code that encounters the errors needs to necessarily know how to handle the error and your app always responds correctly. That said, I don't use exceptions as much in JS because exception handling in JS is still very nascent. There's no base library of exceptions and telling different exceptions apart is not built-in to the language. In a language with more mature exception handling, it's a breeze.
  - austin-cheney 3y ago
    You made the same mistake as the grandparent by assuming I/O means something more specific than it does. At any rate there isn't a good reason to bubble error objects out of the event handler and secondly even if you did you would have everything you need to fully describe the problem within the error object including the stack trace, event type, error message, and so forth. Its an equivalent breeze in JavaScript as well unless you are fumbling through abstraction layers (frameworks) that eliminate the information you need.
    - thrashh 3y ago
      Not at all. You don't have to describe anything when throwing an error because that's the point of exception inheritance. Second, the whole point of exceptions is to bubble them out of the handler(!) because otherwise you would use return values (like in Go). Since you are saying that you have to describe the problem within the error object, it sounds like you must be you are parsing error messages and stack traces to figure out what the error is. That's not how exceptions are to be used and I think that's why you are not seeing why you would bubble errors. In other languages, you don't have to do any of that nonsense because object identity is much stronger, but JavaScript uses prototypical inheritance so you can't really tell if an error is an ImageError or an IOError. Despite this issue, exceptions were added to the JavaScript language without resolving that problem. The reason why you have to worry about frameworks eliminating error information is because that problem wasn't resolved and so frameworks roll their own error handling and there is no standard.

afavour 3y ago

> Also, try/catch will never compile in the JIT Changing the way you program to fit what a JS compiler does or doesn't do is a fool's errand, IMO. The performance benefits are likely to be minimal, confusion for anyone else who has to touch the codebase is high.

madeofpalk 3y ago
And, JS engine's whims change frequently enough that yesterdays micro-optimisation is today's deopt. Much better to just write ideomatic code.
austin-cheney 3y ago
That depends on how many changes it requires. If its just a matter of don't do these 3 things and your code suddenly becomes more predictable its like being slapped with a magic wand. Everybody wins. All you have to do to ensure 100% of your code compiles in a JIT is be predictable. Predictable code is, on its face, always less confusing. > The performance benefits are likely to be minimal This makes me cry, but not a cry of joy or ecstasy. People guessing about performance is perhaps the most frequent anti-pattern in all programming. Please read the following document, you can skip to the end but it may not make much sense if you do. https://github.com/prettydiff/wisdom/blob/master/JavaScript_Made_Simple.md https://github.com/prettydiff/wisdom/blob/master/JavaScript_... When developers make random performance assumptions, defensive assumptions are worse, it immediately identifies a lack of professional maturity. Its like small children playing games that expand their imagination, which is great for small children but less great for developers pretending to be adults.
- afavour 3y ago
  > People guessing about performance is perhaps the most frequent anti-pattern in all programming I disagree, premature optimisation is. Changing your style of programming to suit what todays JIT does but tomorrow’s may not, in anticipation of performance issues you have not yet encountered is a waste of everyone’s time. No doubt it is valuable in extremely performance sensitive code but that is the extreme minority, especially in the JavaScript world. If I were involved in a project where performance concerns were high enough to require everyone know what the JIT is and is not doing my proposal would be to use a language other than JavaScript. If thinking this makes me a “small child” in your mind I’m fine with that.

eyelidlessness 3y ago

> Also, try/catch will never compile in the JIT. If this is an actual concern (as in you have measured and try/catch is actually affecting something performance sensitive): you can most likely mitigate the impact by isolating the try/catch bodies in separate functions. I haven’t verified this in every JIT, but I saw meaningful perf improvement in V8 for real world degenerate cases where the performance did actually matter and make a significant difference. But seriously, as always, measure before optimizing stuff like this! It might matter, but it seldom will for anything more than academic curiosity.

magicalist 3y ago

> Also, try/catch will never compile in the JIT This was only ever true in V8, and hasn't been the case since 2017 with the optimizing compiler switch from Crankshaft to TurboFan. Take a break before lecturing commenters on "guessing about performance is perhaps the most frequent anti-pattern in all programming" next time :)

simlevesque 3y ago

> Also, try/catch will never compile in the JIT That's false. It used to be this way with Crankshaft but since 2017 we have Turbofan which solves this.