filter

filter combinator applies parser and tests its value with the fn predicate. Succeeds with the value if fn returns true, otherwise fails with expected. Failures of parser itself are propagated as is.

Usage

const Port = filter(
  integer(),
  (value) => value >= 0 && value <= 65535,
  'port number'
)

Success

run(Port).with('8080')

{
  isOk: true,
  start: 0,
  end: 4,
  pos: 4,
  value: 8080
}

Failure

run(Port).with('70000')

{
  isOk: false,
  start: 0,
  end: 5,
  pos: 0,
  expected: 'port number'
}