What sort of issues with ES5 are static class methods in ES6 supposed to deal with?
The Babel documentation has the following example in its section regarding ES6 classes, though it does not actually state what this pattern acplishes.
Classes support prototype-based inheritance, super calls, instance and static methods and constructors
class SkinnedMesh extends THREE.Mesh {
constructor(geometry, materials) {
super(geometry, materials);
this.idMatrix = SkinnedMesh.defaultMatrix();
this.bones = [];
this.boneMatrices = [];
//...
}
update(camera) {
//...
super.update();
}
static defaultMatrix() {
return new THREE.Matrix4();
}
}
What sort of issues with ES5 are static class methods in ES6 supposed to deal with?
The Babel documentation has the following example in its section regarding ES6 classes, though it does not actually state what this pattern acplishes.
Classes support prototype-based inheritance, super calls, instance and static methods and constructors
class SkinnedMesh extends THREE.Mesh {
constructor(geometry, materials) {
super(geometry, materials);
this.idMatrix = SkinnedMesh.defaultMatrix();
this.bones = [];
this.boneMatrices = [];
//...
}
update(camera) {
//...
super.update();
}
static defaultMatrix() {
return new THREE.Matrix4();
}
}
-
5
Personally, I use the
statickeyword to indicate to the developer that this method doesn't use information from the current instance - similar to using underscore-prefixed names to indicate private properties - even though that may not necessarily be the case, it's a nice bit of self-menting if used correctly – CodingIntrigue Commented Jun 15, 2015 at 11:38 - Very good example, thanks! – Martin Meeser Commented Apr 14, 2016 at 9:18
- May I suggest to rename 'defaultMatrix' to 'createDefaultMatrix', because it is a very classical 'Factory Method' pattern (encapsulation of 'new' operator), and many agree to that convention. – Martin Meeser Commented Apr 14, 2016 at 9:29
- @MartinMeeser As stated in the question, this code was pulled from Babel's documentation. – Walter Roman Commented Apr 19, 2016 at 19:47
2 Answers
Reset to default 9If you pile ES6 code with Babel, and some class contains a static method, ES5-generated code will be just adding that static function to the constructor function.
So, this ES6 ES2015 code:
class A {
static doStuff() {}
}
...equals (in ES5):
function A() { }
A.doStuff = function() { };
Why you need static functions? Well, transpiled code won't support statics at all, since even functions are objects and static functions are turned into own properties of constructor function.
Static functions or properties can be used to implement factory pattern:
class A {
static create() {
// Specific factory method code
}
}
var instance = A.create();
Anyway, static member usage is a very diffuse topic and it goes out of scope of an objective answer. It has a lot of use cases and these are universal to any programming language.
Consider class that contains only static methods:
class MyNamespace {
static foo() { ... }
static bar() { foo(); }
}
It is quite convenient way of organizing code - put stuff in namespaces.
MyNamespace.foo();
MyNamespace.bar();
That's other than standard static method use cases in other OOP languages.