@neutrium/quantity/src/parsers/NearleyQtyParser.ts

The NeutriumJS unit conversion module.

import Nearley from 'nearley/lib/nearley.js';
import grammar from './qty-grammar.js';
import { QuantityDefinition } from '../QuantityDefinition.js'

export class NearleyQtyParser
{
	constructor() { }

	public parse(val: string) : QuantityDefinition
	{
		// You have to create a new parser each time to reset the state
		const parser = new Nearley.Parser(Nearley.Grammar.fromCompiled(grammar))

		parser.feed(val);

		const results = <QuantityDefinition | undefined>parser.results;

		if(results === undefined)
		{
			throw new Error("Unit not recognized");
		}
		else
		{
			return results[0];
		}
	}
}