I discovered today that this seems to be legal javascript:

class foo {
   a() { console.log( 'a' ); }
   b() { console.log( 'b' ); }
   a() { console.log( 'a2' ); }
}

( new foo() ).a(); // shows a2

The a() function is listed twice, but javascript just ignores the first one. Why is this legal? What is a meaningful use case for this "feature"?