比较函数

function createComparisonFunction(propertyName) {
    return function(obj1, obj2) {
        var value1 = obj1.getAttribute(propertyName),
            value2 = obj2.getAttribute(propertyName);
        if (value1 < value2) {
            return -1;
        } else if (value1 > value2) {
            return 1;
        } else {
            return 0;
        }
    }
}

可用于排序的比较函数