Underscore.js groupBy 多个值 [英] Underscore.js groupBy multiple values

问题描述

使用 Underscore.js，我试图多次对项目列表进行分组，即

Using Underscore.js, I'm trying to group a list of items multiple times, ie

按 SIZE 分组，然后对于每个 SIZE，按 CATEGORY 分组...

Group by SIZE then for each SIZE, group by CATEGORY...

http://jsfiddle.net/rickysullivan/WTtXP/1/

理想情况下，我想要一个函数或扩展 _.groupBy() 以便您可以将数组与要分组的参数一起扔给它.

Ideally, I'd like to have a function or extend _.groupBy() so that you can throw an array at it with the paramaters to group by.

var multiGroup = ['size', 'category'];

可能只是做一个 mixin...

Probably could just make a mixin...

_.mixin({
    groupByMulti: function(obj, val, arr) {
        var result = {};
        var iterator = typeof val == 'function' ? val : function(obj) {
                return obj[val];
            };
        _.each(arr, function(arrvalue, arrIndex) {
            _.each(obj, function(value, objIndex) {
                var key = iterator(value, objIndex);
                var arrresults = obj[objIndex][arrvalue];
                if (_.has(value, arrvalue))
                    (result[arrIndex] || (result[arrIndex] = [])).push(value);

我的头很痛，但我认为这里需要更多的推动......

My head hurts, but I think some more pushing needs to go here...

            });
        })
        return result;
    }
});

properties = _.groupByMulti(properties, function(item) {

    var testVal = item["size"];

    if (parseFloat(testVal)) {
        testVal = parseFloat(item["size"])
    }

    return testVal

}, multiGroup);

推荐答案

一个简单的递归实现:

_.mixin({
  /*
   * @mixin
   *
   * Splits a collection into sets, grouped by the result of running each value
   * through iteratee. If iteratee is a string instead of a function, groups by
   * the property named by iteratee on each of the values.
   *
   * @param {array|object} list - The collection to iterate over.
   * @param {(string|function)[]} values - The iteratees to transform keys.
   * @param {object=} context - The values are bound to the context object.
   * 
   * @returns {Object} - Returns the composed aggregate object.
   */
  groupByMulti: function(list, values, context) {
    if (!values.length) {
      return list;
    }
    var byFirst = _.groupBy(list, values[0], context),
        rest    = values.slice(1);
    for (var prop in byFirst) {
      byFirst[prop] = _.groupByMulti(byFirst[prop], rest, context);
    }
    return byFirst;
  }
});

在你的 jsfiddle 中演示

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