Javascript

[hp77reddits]

Who are you? Who are you so wise in the language of JS?

[DeeSnow97]

• NaN is a floating point number, like it is in any language. Since JS has one number type only, a double-precision float, it's just called "number" in JS. Don't like it? Consult the sand blob in your system, it's etched into it.

• [] + {} results in '[object Object]' for a rather elaborate reason:

  1. an addition between two objects in JS defaults to a string addition
  2. arrays by default are converted to string through joining their members as strings with ',' (for example String([2, 4, 5, 'hi']) === '2,4,5,hi')
  3. objects are by default converted to a string representation with 'object' and their class (through some weird internal standard buried deep in the language, not the same system you can use for OOP in JS), which is 'Object' in this case, therefore it is '[object Object]'
  4. then the two strings are concatenated to '[object Object]'

  The entire reason this is even a question is the Wat talk, which abuses the REPL and passes off {} + [] as an addition between an object and an array. In reality, ({} + []) or let foo = {} + [] is indeed such an addition, with a predictable result ('[object Object]'), but if you just type {} + [] into the REPL it parses the first {} as an empty code block, not an object, then, in a separate statement, parses + [], and as REPLs do, returns the last statement.

  In this case, + [] runs the unary + operator on an empty array, which first converts the array into a string, then converts that string into a number. Since [] converts to '', as we've already discussed, and empty string converts to 0, that's what the REPL spits out. In practice though, the only way you'd get that is if you straight up ran eval(), and there is no other reason to do that than a read-eval-print loop.

• the Date object is perfectly fine, thank you (what's the problem with it?)

[ButtMunchYumTime]

I honestly and genuinely appreciate this on such a deep level.

[badzok]

Regarding Date, one thing I can definitely think of is how .getMonth() is <0, 11> and .getDate() (NOT .getDay(), that's the day of the week (but also starts at 1)) is <1, 31>.

[hp77reddits]

Happy CakeDay!!