用lodash嵌套_.max()

Question

我试图获取对象数组中的数组值的最大值和最小值,如下所示:

[
    {
        id: 1,
        enabled: false,
        layer: 'Mood',
        color: '#f16c63',
        points: [
            {date: '2013-01-02', value: 20},
            {date: '2013-02-02', value: 15},
            {date: '2013-03-12', value: 24},
            {date: '2013-03-23', value: 18},
            {date: '2013-03-24', value: 22},
            {date: '2013-04-09', value: 12},
            {date: '2013-06-13', value: 16},
            {date: '2013-06-14', value: 20},
        ]
    },
    {
        id: 2,
        enabled: true,
        layer: 'Performance',
        color: '#698bfc',
        points: [
            {date: '2013-01-02', value: 15},
            {date: '2013-02-02', value: 24},
            {date: '2013-03-12', value: 29},
            {date: '2013-03-23', value: 21},
            {date: '2013-03-24', value: 20},
            {date: '2013-04-09', value: 17},
            {date: '2013-06-13', value: 25},
            {date: '2013-06-14', value: 21},
        ]
    },
    {
        id: 3,
        enabled: false,
        layer: 'Fatigue',
        color: '#e1fc6a',
        points: [
            {date: '2013-01-02', value: 32},
            {date: '2013-02-02', value: 27},
            {date: '2013-03-12', value: 30},
            {date: '2013-03-23', value: 31},
            {date: '2013-03-24', value: 27},
            {date: '2013-04-09', value: 15},
            {date: '2013-06-13', value: 20},
            {date: '2013-06-14', value: 18},
        ]
    },
    {
        id: 4,
        enabled: true,
        layer: 'Hunger',
        color: '#63adf1',
        points: [
            {date: '2013-01-02', value: 12},
            {date: '2013-02-02', value: 15},
            {date: '2013-03-12', value: 13},
            {date: '2013-03-23', value: 17},
            {date: '2013-03-24', value: 10},
            {date: '2013-04-09', value: 14},
            {date: '2013-06-13', value: 12},
            {date: '2013-06-14', value: 11},
        ]
    },
]

我需要从points数组中获取最大值和最小值.似乎我可以做这样的事情,最大值和类似的最小值:

                   var maxDate = _.max(dataset, function (area) {
                   return _.max(area.points, function (point) {
                       console.log(new Date(point.date).getTime())
                       return new Date(point.date).getTime()
                   })

               });

但由于某种原因,这会让我 - 无限.使用嵌套的_.max()运行是否合法？我使用这种方法与D3.js库工作得很好.

请指教.

Answer 1

内部_.max将返回具有最大日期的点,但是您传递给外部的函数_.max需要一个可以比较的值.比较这些值时,它将返回具有最大值的图层.

听起来你想要从所有可用层中获得最大点(这是正确的)吗？

如果是这样,你可以这样做:

function pointDate(point) {
    console.log(new Date(point.date).getTime())
    return new Date(point.date).getTime()
}

var maxDate = _.max(_.map(dataset, function (area) {
    return _.max(area.points, pointDate);
}), pointDate);

这将返回所有点的最大日期的点对象.

这是一个很好的功能风格的方法:

function pointDate(point) {
    console.log(new Date(point.date).getTime())
    return new Date(point.date).getTime()
}

var maxDate = _(dataset).map('points').flatten().max(pointDate);