week days

days.js

function days(ds) {
	const results = [];
	for (let i = 0; i < ds.length;) {
		// if (i === 0)results.push(days[i]);

		console.log(i);
		const s = i;
		let t = i;
		while (ds[t + 1] && ds[t] && ds[t + 1] - ds[t] === 1) {
			t++;
		}
		i = t;
		i++;
		// results.push(s);

		if (results.length > 0) results.push(',');

		if (t === s) results.push(ds[s]);
		else if (t - s === 1) results.push(ds[s], '-', ds[t]);
		else if (t - s > 1) results.push(ds[s], ' - ', ds[t]);
	}
	return results.join('');
}
console.log(days([ 1, 2, 4, 5, 6 ]));