satisfy

satisfy(fn: function, m?: string): Parser

Parses a character for which the predicate fn returns true when passed that character.

Since the parser cannot reasonably figure out what conditions cause fn to pass, it does not generate an error message on failure by default. To provide a useful error message, supply that message as the optional second argument.

Example

const parser = satisfy(x => x === x.toUpperCase())

const s = parse(parser, 'ABC')
console.log(status(s))  // "ok"
console.log(success(s)) // "A"

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

Parameters

• fn: The predicate function that the next character must pass in order for the parser to succeed.
• m: The optional expected error message that will take the place of the default error message.

Success

• Succeeds if fn returns true when the next character is passed into it. Consumes and returns that character.

Failure

• Fails if fn returns false when the next character is passed into it.

Throws

• Throws an error if fn is not a non-parser function.
• Throws an error if m exists and is not a string.

See Also

• Parser
• range
• regex