I've never worked through my own solution to the infamous "First Unique Character" problem.

firstUnique.js

function firstUnique (str) {
	var hash = {};
	for (var i = 0; i < str.length; i++) {
		hash[str[i]] = hash[str[i]] + 1 || 1;
	}
	for (var i = 0; i < str.length; i++) {
		if (hash[str[i]] === 1) {
			return str[i];
		}
	}
}
console.log(firstUnique('abdaccdz') === 'b');// true
console.log(firstUnique('abaabcad') === 'c');// true