linq.js Dynamic Multilevel Grouping

linq-multilevel-grouping.js

/* Utility functions to create a nested, multilevel grouped, ordered 
 * structure out of a flat array of uniform objects.
 * 
 * usage: result = applyStructure(items, structure);
 *
 * structure is an object of the form:
 * {
 *     group: "propertyName1"
 *     order: ["propertyName1", "propertyName2 DESC", ...]
 *     next: {
 *         group: "propertyName3"
 *         order: ["propertyName3 DESC"]
 *         next: {
 *             // etc
 *         }
 *     }
 * }
 *
 * also see http://jsfiddle.net/Tomalak/xth6ayuo/
 */
 
// Enumerable, definition => Enumerable
function applyOrder(items, definition) {
    var i, prop, prefix, suffix, orderFunc;
    if (!items) return;
    if (!definition) return items;
    for (i = 0; i < definition.length; i++) {
        // definition[i] is either "propertyName" or "propertyName DESC"
        prop = (definition[i] + " ").split(" ");
        prefix = i === 0 ? "OrderBy" : "ThenBy";
        suffix = prop[1].toUpperCase() === "DESC" ? "Descending" : "";
        orderFunc = prefix + suffix;
        items = items[orderFunc]("$." + prop[0]);
    }
    return items;
}
 
// Enumerable, definition => Enumerable
function applyGroup(items, definition) {
    if (!items) return;
    if (!definition) return items;
    items = applyOrder(items, definition.order);
    if (!definition.group) return items;
    return items.GroupBy("$." + definition.group, "", function (key, e) {
        return {
            group: definition.group,
            key: key,
            items: applyGroup(e, definition.then).ToArray()
        };
    });
}
 
// Array, definition => Array
function applyStructure(items, definition) {
    if (!items) return;
    if (!definition) return items;
    return applyGroup(Enumerable.From(items), definition).ToArray();
}