I have please encountered the following example in a book of a declaration of a class inside a function argument, even though I have searched thoroughly online, could not find an explanation, what it does, what is declared, what is passed into the function, and when should I use it if at all (perhaps its a bad practice ?).
Thank you for your help and guidance !
function f(parameter1) {
console.log(parameter1);
}
class ClassA {
}
f(class extends ClassA {
render() {
}
});
In javascript, class is just a syntax sugar for function, and just like function it's a first class value, which can be assigned, passed around etc.
let a = class {
foo() {
console.log('hey')
}
};
new a().foo()
//
function x(klass) {
new klass().bar()
}
x(class {
bar() {
console.log(2)
}
})This is defining an anonymous class (in Java terminology... not sure if that is the correct name for JS). This example is pretty nonsensical. I could see it being used if the function f was accepting a class definition and then instantiated an object using it and proceeded to call methods on the object and perhaps return it. So it could be used in a general factory function.
