clean

clean(p: Parser, m?: string): Parser

Applies a parser and returns the resulting array with null and undefined elements filtered out.

There are a number of parsers (opt is an excellent) that can produce null results. If these results are subsequently put into an array via another parser like seq, it very well could be desirable to remove those null elements from the resulting array. This is what clean does.

clean(p) is an optimized implementation of map(p, x => x.filter(e => e != null)).

Example

const parser = seq(letter(), opt(digit()), letter())

const s = parse(parser, 'abcde')
console.log(status(s))  // "ok"
console.log(success(s)) // ["a",null,"b"]

const r = parse(clean(parser), 'abcde')
console.lgo(status(r))  // "ok"
console.log(success(r)) // ["a","b"]

const f = parse(parser, '')
console.log(status(f))  // "fail"
console.log(failure(f)) // Parse error at (line 1, column 1):
                        //
                        // 
                        // ^
                        // Expected a letter

Parameters

• p: The parser that is applied, which must return an array.
• m: The optional expected error message that will take the place of the default error message.

Success

• Succeeds if p succeeds. Returns the resulting array with null and undefined elements filtered out.

Failure

• Fails if p fails.

Fatal Failure

• Fails fatally if p fails fatally.

Throws

• Throws an error if p is not a parser.
• Throws an error if p succeeds but does not return an array.
• Throws an error if m exists and is not a string.

See Also

• Parser
• map