JavaScript Enum

Enum.js

function Enum(items, startingValue) {
    var count = startingValue || 0,
        item;
    for (var i = 0; i < items.length && (item = items[i]) ; i++) {
        var splitted = item.split(':');
        if (splitted.length == 2) {
            count = Number(splitted[0]);
            item = splitted[1];
        }
        this[this[item] = count++] = item;
    }
    Object.freeze(this);
}

// Usage example:
// var example = new Enum(["MINUS_ONE", "ZERO", "4:FOUR", "FIVE"], -1);