parser.js

A library for building recusive descent parsers by hand, Inspired by dmaevsky/rd-parse.

Functionality

• Automatic AST Generation
• Grammar is written directly in JS using EBNF/Regex-like operators

Remarks

• This library makes use of rest parameters quite extensively to make usage more convenient
• If a match was found the matched values are returned in an array, empty arrays [] indicate success but no matched values
• If no match was found or the match failed undefined is returned

Basic Tokens

CapturingString

CapturingString(value)

• Matches a given string at the current position
• Captures the matched string
• Returns an the matched string in an array or undefined on failure

NonCapturingString

NonCapturingString(value)

• Matches a given string at the current position
• Does not capture anything
• Returns an empty array [] or undefined on failure

Regex

Regex(value)

• Matches a given regex at the current position
• Captures all capturing groups of the regex
• Returns the capturing groups in an array or undefined on failure

Operators/Combinators

All ( , )

All(...fragments)

• Concatenates the given fragments
• Matches the concatenated fragments exactly 1 time
• Returns matched values in an array or undefined on failure

Any ( | )

Any(...fragments)

• Tries all fragments until a matching one is found
• Matches the first matching fragment exactly once
• Returns the first match found in an array or undefined on failure

Optional ( ? )

Optional(...fragments)

• Concatenates the given fragments
• Matches the concatenated fragments 0 to 1 times
• Returns matched values in an array or an empty array [] when no match was found

Repetition ( * )

Repetition(...fragments)

• Concatenates the given fragments
• Matches the concatenated fragments 0 to unlimited times
• Return matched values in an array or empty array [] when no match was found

AtleastOnce ( + )

AtleastOnce(...fragments)

• Concatenates the given fragments
• Matches the concatenated fragments 1 to unlimited times
• Return matched values in an array or undefined on failure

Modifiers

Group

Group(...fragments)

• Concatenates the given fragments
• Returns the matched values as an array inside an array

Reduce

Reduce(reduce, ...fragments)

• Concatenates the given fragments
• Calls the reduce function with matched values as arguments
• If Array.isArray(returnValue) is true, returns the return value as is
• If Array.isArray(returnValue) is false, returns the return value in an array
• On failure, returns undefined

AstNode

AstNode(constructor, ...fragments)

• Concatenates the given fragments
• Instantiates a new object from the given constructor with the matched values as arguments
• Returns the instantiated value in an array or undefined on failure

Whitespace

Whitespace(whitespace, ...fragments)

• Concatenates the given fragments
• Sets the current whitespace fragment for all descending fragments
• returns the matched values in an array or undefined on failure