Underscore.js groupBy具有多个值

Question

使用Underscore.js,我试图多次对项目列表进行分组,即

然后由SIZE分组为每个SIZE,按类别分组......

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

理想情况下,我希望有一个函数或扩展,_.groupBy()以便您可以使用参数对其进行分组.

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

可能只是混合...

_.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,但我觉得还有更多需要去的地方......

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

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

    var testVal = item["size"];

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

    return testVal

}, multiGroup);

Answer 1

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演示

Answer 2

我认为@ Bergi的答案可以通过利用Lo-Dash mapValues (用于在对象值上映射函数)来简化.它允许我们以嵌套的方式通过多个键对数组中的条目进行分组:

_ = require('lodash');

var _.nest = function (collection, keys) {
  if (!keys.length) {
    return collection;
  }
  else {
    return _(collection).groupBy(keys[0]).mapValues(function(values) { 
      return nest(values, keys.slice(1));
    }).value();
  }
};

我将方法重命名为,nest因为它最终提供了与D3的嵌套运算符相同的角色.请参阅此要点以获取详细信息以及此示例中演示用法的小提琴.

lodash nest groupby

Answer 3

这个相当简单的黑客怎么样？

console.log(_.groupBy(getProperties(), function(record){
    return (record.size+record.category);
}));