Comment by zanny
11 years ago
This is more a reflection of how bad the JS language is than anything. Real programming languages have means of standardizing the most common UX and simple patterns into a standard library. Javascript is a consortium hell that never gets updated sufficiently, and has no good standard library, so NPM basically replaces the standard library with a thousand micropackages.
Also it is a lot easier to get it wrong in JS. Is it null? Is it undefined? Is it bird? Is it a plane? No it's a string!(but sometimes a number). Good programming languages make it easy to write is negative e.g. isNegative = (<0) where implicitly by the 0 and < it will take a Num and return a bool and this is type checked at compile time.
Use the null object pattern.
If you're checking a value to see if it's set by testing for null/undefined, you're doing it wrong.
This is good advice for any language, not just JS.
Besides, using null as the default for an undefined value is a mistake. Null should indicate a non-value not the absence of a value. Maybe one day the static OOP languages will die so devs have a chance to learn the difference.
My point is more that the compiler* can't detect these mistakes but in other languages you can. E.g. in Haskell you only allow Null on types when you want it (you do this by using the Maybe type). Objects where you probe for values that could be undefined or could be defined but null doesn't exist as a concept but if you badly wanted it you could use a dictionary. In Haskell if you use Maybe and you process a Maybe object you have to deal with the null and not null case otherwise you get a compiler error.
All these checks seem annoying but we've all seen the bar chart of when you discover the bug vs. the cost of that bug. The compiler finding the bug is cheap. Haskell is a cheap language to program in, compared to JS!
* I forgot there is no compiler in JS but let's say the linter for argument sake.
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