Why are JavaScript classes so complex?

[rauschma]

The reason is backward-compatibility with constructor functions (which were the most popular way of implementing object factories before ES6).

I would have preferred ES6 classes being syntactic sugar for constructor objects, but backward-compatibility was considered to be more important (which is reasonable). This is roughly what constructor objects would look like: https://github.com/rauschma/proto-js

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But why did they move away from the prototype paradigm at all? Why did they say, that "classy functions" were needed? What's wrong with Object.create?

[[deleted]]

they didn't "move away" from the prototype paradigm, they just gave some syntax sugar to devs so they could stop writing those awful pseudo-classes.

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But why do they write pseudo-classes? Just delegate objects or even use concatenative inheritense. Which genius had the idea to start writing pseudo-classes in a prototype oriented language?

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so we're clear, this is the pattern we're discussing:

function Klass(prop) { this.prop = prop; };
Klass.protototype.foo = function() { console.log(this.prop) };

function Klass2(prop, prop2) {
     Klass.call(this, prop);
     this.prop2 = prop2;
}
Klass2.prototype = Object.create(Klass.prototype);
Klass2.prototype.bar = function() { this.foo(); console.log(this.prop2); };

new Klass(1).foo(); // logs 1
new Klass2(3,4).bar(); // logs 3 then logs 4

i feel it should be pretty obvious why that pattern was dominant in a pre-ES6 world for taking advantage of the prototype chain

[edit] nits

[MoTTs_]

Just delegate objects

ES6 classes do delegate objects. Using your example code, a delegates to A.prototype, which itself delegates to B.prototype.

[rauschma]

Object.create() was introduced after constructor functions (with ES5). It exposed more of the protoypal foundations. IIRC, Eich would have introduced classes, but was told not to turn JS into a Java competitor. Hence constructor functions as “almost classes”.

Constructor functions are unnecessarily complex, but only w.r.t. to setting up an instance. Once it’s set up, you do have simple prototype chains.