New JavaScript features do just that: 2) Globals with 'x = 1' throws an error when run in strict mode. 3) They couldn't change the meaning of 'var', but they

New JavaScript features do just that: 2) Globals with 'x = 1' throws an error when run in strict mode. 3) They couldn't change the meaning of 'var', but they introduced 'let' which does just that - applies to a block rather than the whole function.