print alphabet using char codes

abc123.js

function range(x, y) {
	if (typeof y === 'undefined') {
		y = x;
		x = 0;
	}
	let out = [];
	while (x < y) {
		out.push(x++);
	}
	return out;
}

function exclude(first, ...arrs) {
	// Note that Array.prototype.includes will not do deep-equality checks on reference values
	return arrs.reduce((acc, cur) => acc.filter(el => !cur.includes(el)), first);
}

// 48-57 = 0-9
// 65-90 = A-Z
// 97-122 = a-z

let alphaNumCodes = exclude(range(48, 122 + 1), range(58, 65), range(91, 96 + 1));
let alpha = alphaNumCodes.reduce((prev, cur) => prev + String.fromCharCode(cur), '');
console.log(alpha); // '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'