gistfile1.js

// Sort stories by tasks progress, story title and priority
data.stories.data.sort(dynamicSortMultiple("!tasks.progress", "title", "priority"));

function dynamicSort(property) {
    return function(obj1, obj2) {
        var reverse = (property.indexOf("!") === 0);
        var comparisonValue1, comparisonValue2 = '';

        if (reverse) {
            property = property.substr(1);
        }

        if (property.indexOf(".") !== -1) {
            var bits = property.split(".");
            
            comparisonValue1 = obj1[bits[0]][bits[1]];
            comparisonValue2 = obj2[bits[0]][bits[1]];
        } else {
            comparisonValue1 = obj1[property];
            comparisonValue2 = obj2[property];
        }
        
        return reverse
            ? (comparisonValue1 < comparisonValue2 ? 1 : comparisonValue1 > comparisonValue2 ? -1 : 0)
            : (comparisonValue1 > comparisonValue2 ? 1 : comparisonValue1 < comparisonValue2 ? -1 : 0);
    }
}

function dynamicSortMultiple() {
    /**
     * save the arguments object as it will be overwritten note that arguments object
     * is an array-like object consisting of the names of the properties to sort by
     */
    var props = arguments;

    return function(obj1, obj2) {
        var i = 0, result = 0, numberOfProperties = props.length;

        // try getting a different result from 0 (equal) as long as we have extra properties to compare
        while(result === 0 && i < numberOfProperties) {
            result = dynamicSort(props[i])(obj1, obj2);
            i++;
        }

        return result;
    }
}