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I am trying to write a code that is readable and maintainable instead of building complex abstractions. That is where Java classes fit perfectly (unless you are

• chriswarbo 10y ago
  > I am trying to write a code that is readable and maintainable instead of building complex abstractions. My point is that what's "readable and maintainable" depends on the language; especially on what facilities it provides, and to some extent community consensus (what's 'idiomatic'). Javascript's main facilities are first-class functions with lexical scope, lightweight key/value mappings (which it calls "objects") and prototypical inheritance between those objects. Java's main facilities are classes with properties and methods; whilst it's recently gained first-class functions, most Java code has been written without them, and they'll always be in competition with classes+methods (e.g. look at all of the APIs which use single-method classes, like "Comparator"). These are very different, so what's readable/maintainable will differ in each. For example, Javascript's objects are so lightweight that it's idiomatic to write them inline exactly where they're needed, like 'foo({bar: function() { ... }, ...})'. In idiomatic Java, such objects should be instances of a class, which should either be global or else implement a global interface. Since global class/interface declarations require standalone files, our declarations end up very far away from the use site; this prevents us accessing the use-site's scope and puts us under more pressure to make it descriptive, generic, reusable, etc. > Yet Javascript has neither of those. ES6 has a module system, Java has its "package" system. Trying to apply SML practices to either is a bad idea, just as trying to apply Java OO practices to JS is a bad idea, or trying to apply Lisp macro practices to C is a bad idea.
  • codedokode 10y ago
    > For example, Javascript's objects are so lightweight that it's idiomatic to write them inline exactly where they're needed, like 'foo({bar: function() { ... }, ...})'. Idiomatic doesn't mean maintainable and scalable. Imagine you are working on a project in a team, not alone. How do you understand what kind of "lightweight" object you should pass to this function: function foo(data) { .. } When you have thousands of such functions you'll spend most time reading through their code to understand what type of argument they need. This means "idiomatic" javascript code works only when it is small in size. Once it gets larger you'll have to resort to old school non-idiomatic Java-like classes and a static typing system. Regarding prototypal inheritance I don't understand how it is supposed to be used. Let's say we have constructors for objects User(name) and SuperUser(name, privileges). I understand if `SuperUser` is inherited from `User` (class-based ineritance), but I don't understand what is the meaning of SuperUser being inherited from some user charlie. Why `charlie` and not `john`? Why do I need an instance of common `User` to create a `SuperUser`? And as I haven't seen the explanation in above comments I guess you don't understand it too yet evangelize about it. I think JS was supposed not to have any inheritance at all. The objects were supposed to be created with constructors and that is all. As an argument I can say that a helper method `Object.create()` that is required for object inheritance was only added in ES5 [1] and haven't existed in earlier versions. This is how you create objects from objects without classes and even without constructors: var person = { name: null, greet: function () { ... } }; var john = Object.create(person, { name: 'John' }); var charlie = Object.create(person, { name: 'Charlie' }); var superCharlie = Object.create(charlie, { isSuperUser: true }); I also guess JS doesn't have classes because it was designed for writing simple form validation scripts and not large applications. [1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
    • qwertyuiop924 10y ago
      >How do you understand what kind of "lightweight" object you should pass to this function ...and this is where well-documented interfaces come in. >but I don't understand what is the meaning of SuperUser being inherited from some user charlie. That was merely an example to express the difference: the idea is, instead of writing a class and doing things that way, objects are cloned from one another. If you want to create a user with special powers, you clone the user object (usually running a constructor function along the way) and give it whatever new functions you want. If you want to create more of these special users, you make them all have that one as a prototype. Typically, the prototype object is never actually used or altered from the defaults, as this would be confusing, and is given a constructor function to instantiate state. But it doesn't have to be. >I think JS was supposed not to have any inheritance at all. The objects were supposed to be created with constructors and that is all. Wrong. Object.create may be new, but prototypical inhertance is an important par of how the constructors you claim to be the way objects were meant to be created work. Function.prototype, the property which determines the prototype of objects created by a constructor, dates back to ES1. >I also guess JS doesn't have classes because it was designed for writing simple form validation scripts and not large applications.I also guess JS doesn't have classes because it was designed for writing simple form validation scripts and not large applications. Also complete nonsense. Prototypical inheritance was originally implemented in Self, a system developed my Sun Microsystems, and a descendant of Smalltalk-80, which certainly was designed for large applications. JS may have been built for writing simple for validation scripts, and it may be a deeply flawed language in some respects, but the fundamentals of the language, prototypical inheritance, true first-class functions, and lexical scoping, are all things that Eich got right. And given first class functions and lexical scope are still things that language designers have trouble getting right (I've got nothing against class-based OO, so I'm not including it here), it's even more remarkable that Eich did it properly in 1997.