7 ms·

The WHY of WAT - understanding why 'JavaScript is Crazy'

82 points by amirhhz 15y ago

shdon 15y ago
The original presentation was nicely done, but knowing how things work in JavaScript (even though I don't know Ruby) meant I didn't exactly have that WTF-experience. This article explains it nicely to those who had.
- VMG 15y ago
  I think this kind of misses the point. Even if you understand why JavaScript behaves this way, it doesn't mean that the behavior is sane. JavaScript without type coercion would have been safer and saner in my opinion.
  - dexen 15y ago
    Type coertion is a language feature just like some other risky-yet-helpfull features. Take for example pointers: any programming language without pointer is safer†, but pointers help you express certain things concisely and thus avoid some classes of bugs. Heck, a knife with dull blade is safer just as well, but that doesn't increase its overall utility. Compare with: > UNIX was not designed to stop its users from doing stupid things, as that would also stop them from doing clever things. — Doug Gwyn -- †except that you can generate NullPtrException in the pointerless Java. Ask yourself, WAT?
    - bricestacey 15y ago
      Nitpick: dull blades are not safer.
      - zecho 15y ago
        Sub-nitpick: Depends on how you're handling the blade. A dull blade on a round onion is not safer than a sharp blade on that onion. Running your hand across a dull blade is safer than running your hand against a sharp blade. Javascript in a nutshell.
    - spacemanaki 15y ago
      Nitpick: Java does have pointers in the sense of indirect references, so it makes perfect sense that a NullPointerException can exist, even if having nullable references in general is a bad idea.
      - lmm 15y ago
        Java has references but not pointers, in that you can't do arithmetic with them. This actually does increase safety substantially; you can still get a (badly-named) exception by trying to dereference a null reference, but it's a lot harder to turn what was supposed to be a pointer to an input buffer into a pointer to your program's executable code.
    - VMG 15y ago
      Pointer are incredibly more useful than type coercion. In my experience, it is only really useful for beginners who then don't have to know that "1" and 1 are different things. JavaScript has a basically useless == operator because of this.
    - gambler 15y ago
      That's awfully generic and doesn't address the criticism. What are the examples of useful type coertion? What do they achieve? Are there no better ways to achieve those same goals without introducing bug-prone, WAT-inducing behaviors? For example, string concatenation could have been handled by a separate operator.
      - prodigal_erik 15y ago
        To be fair, Eich was required to imitate java and finish in a couple of weeks for marketing reasons, and string + int -> string was one of java's mistakes.
    - gurkendoktor 15y ago
      Knowing C but not JavaScript, I can think of uses for all operations that are defined on C pointers. Yet, I cannot come up with one for String - Number or Hash + Array. If you want to argue that they are useful shortcuts, I think examples would help the case.
      - pabloPXL 15y ago
        Well I think that was 'designed' basically to cast any type to it's string representation. Also wanted to point that I used type coercion when is supposed to be used, and never got a bug of that nature in my code, but yes, you must get the coercion rules right from the beginning, and yes, javascript code could live perfectly with this 'feature'.
vmind 15y ago
This is only part of the why. The other part is the valueOf function which you can specify in order to control what the value of an object is when coerced. So for instance: var arr1 = [1,2,3], arr2 = [1,2,3,4]; console.log(arr1 + arr2); // "1,2,31,2,3,4" arr1.valueOf = function () { return this.length; }; arr2.valueOf = arr1.valueOf; console.log(arr1 + arr2); // 7
rdtsc 15y ago
> ... he pokes fun at some apparently crazy behaviours in Ruby and Javascript. I am sorry, but that still is crazy behavior. You can excuse it with a historical perspective ("well it had to hide errors from users") or by explaining "the why" like you do, that still doesn't make that behavior less crazy.
- karterk 15y ago
  Not trying to defend the craziness, but, when you are trying to do []+{} and "foo"-1, you can kinda expect unexpected results if you know that JS does type coercion.
  - jlouis 15y ago
    That is not the problem here. The problem is that this might by the code piece "x + y" where x and y is in your scope and happens to be [] and {}. The resulting value is then highly confusing to a programmer. A language that enforces explicit type conversion (some call these strongly typed languages) would not allow this, but require you to write something like "string(x) + string(y)" if you really wanted such behaviour. I think it is rather bad semantics actually.
    - ricardobeat 15y ago
      I can't imagine a single situation where you expect variables used in a sum operation to be arrays/objects. That would be highly confusing. You always have the option to use Number(x) + Number(y) (+x) + (+y) String(x) + String(y)
      - jerf 15y ago
        "I can't imagine a single situation where you expect variables used in a sum operation to be arrays/objects." That's precisely the problem. You don't expect them, but there's nothing to prevent it from happening, so it does. Your proposed solutions don't solve the problem, they occur too late. By the time you're adding together two non-numbers (and non-strings) you've already lost, trying desperately to cast them to numbers first is also wrong, along with so verbose that nobody will ever do it.
logn 15y ago
The syntax doesn't bug me too much. Most of it is documented fairly well. The craziest thing about JavaScript is a lack of any good online reference for their classes and methods. JavaScript documentation usually just resorts to a key example or a brief description without covering all the details.
- phoboslab 15y ago
  Mozilla's MDN is great: https://developer.mozilla.org/en/JavaScript/Reference https://developer.mozilla.org/en/JavaScript/Reference
  - jacobolus 15y ago
    Add “MDN” to any javascript-related google query to get the MDN page at the top of the results page. Examples: “operator precedence mdn”, “string mdn”, “slice mdn”.
- Achshar 15y ago
  I always end up googling what i need and i find it rather easily. I find it more easy to fill in my query with keywords ans answer is usually in top5 results :)
Achshar 15y ago
Well i'v never understood the problems with JavaScript but maybe it's because i haven't done things how other languages do it. But js is very "open" and bound free. Especially with functions and objects. They make sense to someone who is new to OOP. maybe its not follow how things are usually done in other languages but that does not mean its necessarily a bad thing. If you think something doesn't make sense that does not mean its wrong. i am learning c and i have to say typed variables must be faster but they are difficult to gasp at first. In fact its a nightmare to make variables of a certain type, it limits my thought process when i have to think what the variable's type is after every line of code. Strings look like a huge deal. The fact that i have to predetermine the length of a string is laughable. Its my string and it can be as long as i want it to be anywhere in my code. (yes i now sound immature but this is my experience until now, call it a rant if you may) Alot of things need to be known before we can write a meaningful program. Thats not the case with js or even with php to some extent.
- Peaker 15y ago
  These difficulties in C are not "craziness", they are for very good reasons. Unbounded strings have much more complex and potentially less optimal semantics than bounded strings, need to be allocated in different ways, etc. C makes tight resource control possible, and to do that it sacrifices a lot of ease. You have to think about resources when programming. In many scenarios, this is a good thing.
  - Achshar 15y ago
    Yes, i agree. I was not offending C, i was just defending JS buy using C as an example. I have said this below but will say again. C is as much crazy to me as is JS to some other people. this does not make C evil.
  - slowpoke 15y ago
    >C makes tight resource control possible, and to do that it sacrifices a lot of ease. I'm not a C programmer (yet), but I would say that depends on what you define as "easy" or "simple". What I am is an Arch Linux user, and I embrace KISS - Keep It Simple, Stupid. Arch understands "simple" as "technically elegant and uncomplicated", but that doesn't mean it's easy to understand or foolproof to use - for the inexperienced user, that is. C is an incredibly powerful tool exactly because it is this kind of simple. What I also am is someone who learned programming with Python, and I initially couldn't understand the appeal of C-oid languages either. But I've since realized it's all about using the right tool for the job. A programmer is a mechanic, and a mechanic that only knows how to use a hammer is a pretty useless mechanic (in general, of course. If all you deal with are nails then it's not an impediment to your abilities).
bdg 15y ago
>Error establishing a database connection Does anyone have a mirror?
- amirhhz 15y ago
  Yes, sorry, Caplin server's didn't expect the load! It's being worked on.
bilalhusain 15y ago
text only cache, courtesy google: http://webcache.googleusercontent.com/search?q=cache:http://blog.caplin.com/2012/01/27/the-why-of-wat/&hl=en&strip=1 http://webcache.googleusercontent.com/search?q=cache:http://... and a duckduckgo tip !cache http://blog.caplin.com/2012/01/27/the-why-of-wat/
- nailer 15y ago
  Full version cache, so the lines aren't unreadably long: http://webcache.googleusercontent.com/search?q=cache:http://blog.caplin.com/2012/01/27/the-why-of-wat/&hl=en&strip=0 http://webcache.googleusercontent.com/search?q=cache:http://...
gambler 15y ago
This is not "WHY", this is "HOW exactly". I bet the reason why JavaScript has these behaviors is due it being developed as a browser scripting language. Authors didn't want the entire script terminating because some part of it was buggy. This could have been handled by some clever isolation and error-recovery mechanism, but it wasn't. Probably due to time constraints. These kinds of things are one of the reasons why I really don't like the idea of everything (including server-side and standalone apps) being written in JavaScript.
- pfraze 15y ago
  That's fair, but PHP has the same level of WTF, and is (I'd argue) less elegant than JS.
  - archgoon 15y ago
    Sorry, I'm missing something. Is the grandparent a big advocate of PHP? Why is PHP being brought into this?
    - pfraze 15y ago
      It's a language that is heavily used for server apps, which the top post was saying JS shouldn't do. My point was, quirks like these haven't outweighed the advantages of PHP, and I don't think they should for JS either.
      - deleted 15y ago
        [deleted]
geraldalewis 15y ago
> It can be a prefix ‘this number is positive’ operator where it operates on a single number. `+` in this context is the "Unary + Operator" which coerces a value to a number via the internal `toNumber` method of the operand. It doesn't make the number positive: node> +-1 // -1
hcarvalhoalves 15y ago
Automatic type coercion feels like a double-barreled shotgun, with one of the barrels pointed back at you: 0. Is only marginally useful 1. You have to be careful with what are you loading, and where 2. Will sooner or later blow up in your face
onfocusin 15y ago
don't explain it! you are killing the fun...

82 points by amirhhz 15y ago

shdon 15y ago

The original presentation was nicely done, but knowing how things work in JavaScript (even though I don't know Ruby) meant I didn't exactly have that WTF-experience. This article explains it nicely to those who had.

VMG 15y ago
I think this kind of misses the point. Even if you understand why JavaScript behaves this way, it doesn't mean that the behavior is sane. JavaScript without type coercion would have been safer and saner in my opinion.
- dexen 15y ago
  Type coertion is a language feature just like some other risky-yet-helpfull features. Take for example pointers: any programming language without pointer is safer†, but pointers help you express certain things concisely and thus avoid some classes of bugs. Heck, a knife with dull blade is safer just as well, but that doesn't increase its overall utility. Compare with: > UNIX was not designed to stop its users from doing stupid things, as that would also stop them from doing clever things. — Doug Gwyn -- †except that you can generate NullPtrException in the pointerless Java. Ask yourself, WAT?
  - bricestacey 15y ago
    Nitpick: dull blades are not safer.
    - zecho 15y ago
      Sub-nitpick: Depends on how you're handling the blade. A dull blade on a round onion is not safer than a sharp blade on that onion. Running your hand across a dull blade is safer than running your hand against a sharp blade. Javascript in a nutshell.
  - spacemanaki 15y ago
    Nitpick: Java does have pointers in the sense of indirect references, so it makes perfect sense that a NullPointerException can exist, even if having nullable references in general is a bad idea.
    - lmm 15y ago
      Java has references but not pointers, in that you can't do arithmetic with them. This actually does increase safety substantially; you can still get a (badly-named) exception by trying to dereference a null reference, but it's a lot harder to turn what was supposed to be a pointer to an input buffer into a pointer to your program's executable code.
  - VMG 15y ago
    Pointer are incredibly more useful than type coercion. In my experience, it is only really useful for beginners who then don't have to know that "1" and 1 are different things. JavaScript has a basically useless == operator because of this.
  - gambler 15y ago
    That's awfully generic and doesn't address the criticism. What are the examples of useful type coertion? What do they achieve? Are there no better ways to achieve those same goals without introducing bug-prone, WAT-inducing behaviors? For example, string concatenation could have been handled by a separate operator.
    - prodigal_erik 15y ago
      To be fair, Eich was required to imitate java and finish in a couple of weeks for marketing reasons, and string + int -> string was one of java's mistakes.
  - gurkendoktor 15y ago
    Knowing C but not JavaScript, I can think of uses for all operations that are defined on C pointers. Yet, I cannot come up with one for String - Number or Hash + Array. If you want to argue that they are useful shortcuts, I think examples would help the case.
    - pabloPXL 15y ago
      Well I think that was 'designed' basically to cast any type to it's string representation. Also wanted to point that I used type coercion when is supposed to be used, and never got a bug of that nature in my code, but yes, you must get the coercion rules right from the beginning, and yes, javascript code could live perfectly with this 'feature'.

vmind 15y ago

This is only part of the why. The other part is the valueOf function which you can specify in order to control what the value of an object is when coerced. So for instance: var arr1 = [1,2,3], arr2 = [1,2,3,4]; console.log(arr1 + arr2); // "1,2,31,2,3,4" arr1.valueOf = function () { return this.length; }; arr2.valueOf = arr1.valueOf; console.log(arr1 + arr2); // 7

rdtsc 15y ago

> ... he pokes fun at some apparently crazy behaviours in Ruby and Javascript. I am sorry, but that still is crazy behavior. You can excuse it with a historical perspective ("well it had to hide errors from users") or by explaining "the why" like you do, that still doesn't make that behavior less crazy.

karterk 15y ago
Not trying to defend the craziness, but, when you are trying to do []+{} and "foo"-1, you can kinda expect unexpected results if you know that JS does type coercion.
- jlouis 15y ago
  That is not the problem here. The problem is that this might by the code piece "x + y" where x and y is in your scope and happens to be [] and {}. The resulting value is then highly confusing to a programmer. A language that enforces explicit type conversion (some call these strongly typed languages) would not allow this, but require you to write something like "string(x) + string(y)" if you really wanted such behaviour. I think it is rather bad semantics actually.
  - ricardobeat 15y ago
    I can't imagine a single situation where you expect variables used in a sum operation to be arrays/objects. That would be highly confusing. You always have the option to use Number(x) + Number(y) (+x) + (+y) String(x) + String(y)
    - jerf 15y ago
      "I can't imagine a single situation where you expect variables used in a sum operation to be arrays/objects." That's precisely the problem. You don't expect them, but there's nothing to prevent it from happening, so it does. Your proposed solutions don't solve the problem, they occur too late. By the time you're adding together two non-numbers (and non-strings) you've already lost, trying desperately to cast them to numbers first is also wrong, along with so verbose that nobody will ever do it.

logn 15y ago

The syntax doesn't bug me too much. Most of it is documented fairly well. The craziest thing about JavaScript is a lack of any good online reference for their classes and methods. JavaScript documentation usually just resorts to a key example or a brief description without covering all the details.

phoboslab 15y ago
Mozilla's MDN is great: https://developer.mozilla.org/en/JavaScript/Reference https://developer.mozilla.org/en/JavaScript/Reference
- jacobolus 15y ago
  Add “MDN” to any javascript-related google query to get the MDN page at the top of the results page. Examples: “operator precedence mdn”, “string mdn”, “slice mdn”.
Achshar 15y ago
I always end up googling what i need and i find it rather easily. I find it more easy to fill in my query with keywords ans answer is usually in top5 results :)

Achshar 15y ago

Well i'v never understood the problems with JavaScript but maybe it's because i haven't done things how other languages do it. But js is very "open" and bound free. Especially with functions and objects. They make sense to someone who is new to OOP. maybe its not follow how things are usually done in other languages but that does not mean its necessarily a bad thing. If you think something doesn't make sense that does not mean its wrong. i am learning c and i have to say typed variables must be faster but they are difficult to gasp at first. In fact its a nightmare to make variables of a certain type, it limits my thought process when i have to think what the variable's type is after every line of code. Strings look like a huge deal. The fact that i have to predetermine the length of a string is laughable. Its my string and it can be as long as i want it to be anywhere in my code. (yes i now sound immature but this is my experience until now, call it a rant if you may) Alot of things need to be known before we can write a meaningful program. Thats not the case with js or even with php to some extent.

Peaker 15y ago
These difficulties in C are not "craziness", they are for very good reasons. Unbounded strings have much more complex and potentially less optimal semantics than bounded strings, need to be allocated in different ways, etc. C makes tight resource control possible, and to do that it sacrifices a lot of ease. You have to think about resources when programming. In many scenarios, this is a good thing.
- Achshar 15y ago
  Yes, i agree. I was not offending C, i was just defending JS buy using C as an example. I have said this below but will say again. C is as much crazy to me as is JS to some other people. this does not make C evil.
- slowpoke 15y ago
  >C makes tight resource control possible, and to do that it sacrifices a lot of ease. I'm not a C programmer (yet), but I would say that depends on what you define as "easy" or "simple". What I am is an Arch Linux user, and I embrace KISS - Keep It Simple, Stupid. Arch understands "simple" as "technically elegant and uncomplicated", but that doesn't mean it's easy to understand or foolproof to use - for the inexperienced user, that is. C is an incredibly powerful tool exactly because it is this kind of simple. What I also am is someone who learned programming with Python, and I initially couldn't understand the appeal of C-oid languages either. But I've since realized it's all about using the right tool for the job. A programmer is a mechanic, and a mechanic that only knows how to use a hammer is a pretty useless mechanic (in general, of course. If all you deal with are nails then it's not an impediment to your abilities).

bdg 15y ago

>Error establishing a database connection Does anyone have a mirror?

amirhhz 15y ago
Yes, sorry, Caplin server's didn't expect the load! It's being worked on.

bilalhusain 15y ago

text only cache, courtesy google: http://webcache.googleusercontent.com/search?q=cache:http://blog.caplin.com/2012/01/27/the-why-of-wat/&hl=en&strip=1 http://webcache.googleusercontent.com/search?q=cache:http://... and a duckduckgo tip !cache http://blog.caplin.com/2012/01/27/the-why-of-wat/

nailer 15y ago
Full version cache, so the lines aren't unreadably long: http://webcache.googleusercontent.com/search?q=cache:http://blog.caplin.com/2012/01/27/the-why-of-wat/&hl=en&strip=0 http://webcache.googleusercontent.com/search?q=cache:http://...

gambler 15y ago

This is not "WHY", this is "HOW exactly". I bet the reason why JavaScript has these behaviors is due it being developed as a browser scripting language. Authors didn't want the entire script terminating because some part of it was buggy. This could have been handled by some clever isolation and error-recovery mechanism, but it wasn't. Probably due to time constraints. These kinds of things are one of the reasons why I really don't like the idea of everything (including server-side and standalone apps) being written in JavaScript.

pfraze 15y ago
That's fair, but PHP has the same level of WTF, and is (I'd argue) less elegant than JS.
- archgoon 15y ago
  Sorry, I'm missing something. Is the grandparent a big advocate of PHP? Why is PHP being brought into this?
  - pfraze 15y ago
    It's a language that is heavily used for server apps, which the top post was saying JS shouldn't do. My point was, quirks like these haven't outweighed the advantages of PHP, and I don't think they should for JS either.
    - deleted 15y ago
      [deleted]

geraldalewis 15y ago

> It can be a prefix ‘this number is positive’ operator where it operates on a single number. `+` in this context is the "Unary + Operator" which coerces a value to a number via the internal `toNumber` method of the operand. It doesn't make the number positive: node> +-1 // -1

hcarvalhoalves 15y ago

Automatic type coercion feels like a double-barreled shotgun, with one of the barrels pointed back at you: 0. Is only marginally useful 1. You have to be careful with what are you loading, and where 2. Will sooner or later blow up in your face

onfocusin 15y ago

don't explain it! you are killing the fun...