case_matching.sjs

macro _match_cond {
    rule {$o($field)} => {
        (typeof $o.$field !== 'undefined')
    }
    rule {$o($field $rest...)} => {
        _match_cond $o($field) && _match_cond $o($rest...)
    }
}
macro _match_var {
    rule {$o($field)} => {
        var $field = $o.$field;
    }
    rule {$o($field $rest...)} => {
        _match_var $o($field)
        _match_var $o($rest...)
    }
}
macro match {
    rule {$tomatch:expr {
            $({
                $field: ident(, )...
            } => {
                $body...
            })...}
        } => {
            var obj = $tomatch;
            $(
                if (_match_cond obj($field...)) {
                    _match_var obj($field...)
                    $body...
                })...
        }
}



match { id: "myid", foo: 42 } {
  { id, foo } => {
    log(id);
    log(foo + 24);
  } {
    id
  } => {
    log(id)
  }
}