Parses strings according to a given metasyntax, providing a cleaner way to parse user input into numbers, booleans, dates, and other objects. Easy to learn, easy to use, and a configurable behaviour topped with custom types and aliases.

Installation and Usage

# Install with NPM:
$ npm install @cursorsdottsx/metasyntax

# or alternatively, with Yarn:
$ yarn add @cursorsdottsx/metasyntax

// Available with CommonJS:
const Metasyntax = require("@cursorsdottsx/metasyntax");

// or with ESM:
import Metasyntax from "@cursorsdottsx/metasyntax";

Documentation

Class Metasyntax

new Metasyntax(metasyntax, options?)

• metasyntax – The metasyntax to parse.
• options – Options for the instance.
  • $ – Placeholder for a string literal.
  • types – Define custom types to use.
    • [type: string]: RegExp | [RegExp, (match: string) => unknown]
  • aliases – Define custom type aliases.
    • [alias: string]: string
  • strict – Strict parsing.
  • partial – Partial parsing.
  • case – Case insensitive parsing.

Creates a new Metasyntax instance.

Metasyntax.prototype.test(target)

• target – Target to test.

Returns true if the target matches the metasyntax, false if otherwise.

Metasyntax.prototype.exec(target)

• target – Target to parse.

Returns an array of parsed values from the target.

Typings

This library comes with default typings that are extremely general but work well enough for both JavaScript and TypeScript users.

However, @cursorsdottsx/metasyntax comes with a typings file that parses metasyntax using types to provide fine and accurate types for Metasyntax. This parser will obviously slow down your language server, so it is optional. To opt in, add ./node_modules/@cursorsdottsx/metasyntax/types.d.ts to your include paths in your tsconfig.json. You can also fiddle with the typings and typeRoots options if the above does not work. Finally, if all has failed, there is still the triple-slash directive to reference it.

If you are using the optional parser, please use as const with the options for finer types.

// Examples of the parser in action:

new Metasyntax("[string] $ <number>", {
    $: "dollar",
} as const).exec("'some string' dollar 1234");
// => [string | undefined, "dollar", number] | undefined

new Metasyntax("[string] $ <number>").exec("'some string' dollar 1234");
// => [string | undefined, {
//        error: "TypeError: Special symbol '$' requires a value to be used."
//    }, number] | undefined

// The parser also works with all the other options, including `aliases` and `types`.

Metasyntax

This flavor of metasyntax is very easy to use and remember. There are only a few simple guidelines and rules.

General syntax:

<type|'literal'|"literal"|type()>
[type|'literal'|"literal"|type()]
$

Operators:

| Operator | Description | | -------- | ------------------- | | <...> | Required arguments. | | [...] | Optional arguments. |

Default types:

| Identifier | Type | Description | | ----------- | ----------- | ------------------------------------------------------------- | | string | string | A string wrapped in ' or " (escape with \). | | number | number | A number in decimal form. | | boolean | boolean | A boolean (only true or false). | | integer | number | An integer in decimal form. | | bigint | bigint | A BigInt instance. | | any | string | Any string of characters that isn't a space. | | char | string | Any character that isn't a space. | | undefined | undefined | undefined | | null | null | null | | date | Date | A date (in ISO form). | | duration | number | Any duration parsable by ms | | regex | RegExp | A regular expression. |

Symbols:

| Symbol | Description | | ------ | --------------------------------- | | $ | Placeholder for a string literal. |

More:

• For array types, use () followed by the default type. Array types must be last and can be optional.

• Array types can't be nested (type()() is not allowed).

• Aliases cannot include other aliases to prevent an infinite loop.

Known bugs or issues

None! If you know one, please submit an issue to get it fixed!