The "statements vs expressions" response would be a neat answer, but then why are commas used for object declaration

let obj = {prop_a: 1, prop_b: 2}

while semicolons are used for class declaration

class Obj {prop_a: 1; prop_b: 2}

?

Declaring the object with a semicolon throws the SyntaxError Unexpected token ';', while declaring the class with a comma throws a different SyntaxError Unexpected identifier 'prop_a'.