@webfeet/microsyntaxes

Implements the HTML common microsyntaxes.

TODO

Currently, only enumerated attributes and numbers are implemented, no dates and times, colors, space- or comma-separated tokens, or references.

API

All parsing functions take a single string or null argument, and return that value parsed according to the specific rules.

enumerated(options)(value)

This function is a factory returning a parser function implementing the rules for determining the state of an enumerated attribute.

The factory functions takes an object as argument with options as properties:

• keywords: mandatory; the list of canonical keywords (those values that will be returned by the parser function)
• aliases: optional; an object associating aliases to their canonical keyword equivalent
• missing: optional; the missing value default (must be a canonical keyword), returned when the parser function is called with null
• invalid: optional; the invalid value default (must be a canonical keyword), returned when the parser function is called with an unknown value

The parser function (returned by the factory function) takes a single string or null argument and returns one of the canonical keywords (or null if missing or invalid are null).

For example, the shape attribute of <area> elements could be implemented as:

const parseShape = enumerated({
  keywords: ["circle", "default", "poly", "rect"],
  aliases: {
    circ: "circle",
    polygon: "poly",
    rectangle: "rect",
  },
  missing: "rect",
  invalid: "rect",
});
parseShape(null); // → "rect"
parseShape("circle"); // → "circ"

parseInteger(value)

This function implements the rules for parsing integers. It takes a single string or null argument and returns a number value, or null if the argument cannot be parsed.

parseNonNegativeInteger(value)

This function implements the rules for parsing non-negative integers. It takes a single string or null argument and returns a number value, or null if the argument cannot be parsed.

parseDouble(value)

This function implements the rules for parsing floating-point number values. It takes a single string or null argument and returns a number value, or null if the argument cannot be parsed.