Functions for validating and normalising postcodes

postcode.js

const postcodeRegex = /^[a-z]{1,2}\d[a-z\d]?\s*\d[a-z]{2}$/i;
const incodeRegex = /\d[a-z]{2}$/i;

const isValidPostcode = (p) => postcodeRegex.test(p.replace(/\s/g, ''));

const normalisePostcode = (p) => {
  if (!isValidPostcode(p)) throw new Error('Invalid postcode');

	const spaceless = p.replace(/\s/g, '');

	const incode = spaceless.match(incodeRegex)[0].toUpperCase();
	const outcode = spaceless.replace(incodeRegex, '').toUpperCase();

	return `${outcode} ${incode}`;
};