Why wrap a class in a var?

Question

What does example B give you that example A doesn't?

EXAMPLE A

class Rectangle {
constructor(height, width) {
this.height = height;
this.width = width;
}
}

EXAMPLE B

var Rectangle = class {
constructor(height, width) {
this.height = height;
this.width = width;
}
}

Answer 1

Considering only your code samples, there's no benifits to use B (class expression) against A (class declaration)... but that's only the simplest use case of class expressions: the real benefits would come with the fact that a class expression could be used anywhere an expression could be used, as the name suggest ;)

You could say that's almost a taste question, but a few more realistic case would be one where the class expression give advantage over equivalent done with class declaration:

// expressions assigned to object properties (namespace):

const shapes = {
Rect: class {
constructor(x,y,w,h) {}
},
Disc: class {
constructor(x,y,r) {}
},
};

// declaration force to declare classes outside, and assign them to object properties after (much verbose, less readable, and potentially pollute global scope unless you wrap all stuff in an IIFE):

class Rect {
constructor(x,y,w,h) {}
}
Disc: class {
constructor(x,y,r) {}
}

const shapes = {
Rect: Rect,
Disc: Disc,
};