Javascript ES6: how to get subclass call from static method defined in superclass
New to JavaScript.
Looking for some guidance on how to access the called class name from a static method defined in a superclass using ES6 classes. I spent an hour searching but couldn't find a solution.
The code snippet might help clarify what I am looking for.
class SuperClass {
get callingInstanceType() { return this.constructor.name }
static get callingClassType() { return '....help here ...' }
}
class SubClass extends SuperClass { }
let sc = new SubClass()
console.log(sc.callingInstanceType) // correctly prints 'SubClass'
console.log(SubClass.callingClassType) // hoping to print 'SubClass'
As shown above, I can easily get the subclass name from the instance. Not really sure how to access the static method.
Ideas for implementation are welcome static get callingClassType()
.
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callingClassType
is a function (well, the getter is the same in this case). The meaning this
inside the function depends on how it is called. If you call a function with foo.bar()
, then this
internally it bar
will refer to foo
.
Thus, if you "call" a function using SubClass.callingClassType
, it this
will refer to SubClass
. SubClass
itself is a (constructor), so you can get its name using a property name
.
So your method definition should be
static get callingClassType() { return this.name; }
class SuperClass {
get callingInstanceType() {
return this.constructor.name
}
static get callingClassType() {
return this.name
}
}
class SubClass extends SuperClass {}
let sc = new SubClass()
console.log(sc.callingInstanceType)
console.log(SubClass.callingClassType)
Take a look at the MDN documentation to learn more aboutthis
.
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Use SuperClass.prototype.constructor.name
:
class SuperClass {
get callingInstanceType() { return this.constructor.name }
static get callingClassType() { return SuperClass.prototype.constructor.name; }
}
class SubClass extends SuperClass {}
class SubClass2 extends SuperClass {
static get callingClassType() { return SubClass2.prototype.constructor.name; }
}
console.log(SuperClass.callingClassType); // 'SuperClass'
console.log(SubClass.callingClassType); // 'SuperClass'
console.log(SubClass2.callingClassType); // 'SubClass2'
From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/static#Examples :
class Triple {
static triple(n) {
if (n === undefined) {
n = 1;
}
return n * 3;
}
}
class BiggerTriple extends Triple {
static triple(n) {
return super.triple(n) * super.triple(n);
}
}
console.log(Triple.triple()); // 3
console.log(Triple.triple(6)); // 18
var tp = new Triple();
console.log(BiggerTriple.triple(3));
// 81 (not affected by parent instantiation)
console.log(tp.triple());
// 'tp.triple is not a function'.
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