javascript - 使用 Underscore.js 合并/组合和求和数组条目

Question

我有 2 个 JSON 对象数组，我希望将它们合并/组合在一起，然后总结所有匹配条目的数量。

两个数组都包含相同的结构，一个表示需要使用的设备列表...

var required = [
    { SerialisedEquipment: { SerialNo: "ser855212" }, Type: undefined, Serialised: true, Quantity: 1 },
    { SerialisedEquipment: { SerialNo: "ser288945" }, Type: undefined, Serialised: true, Quantity: 1 },
    { SerialisedEquipment: undefined, Type: { ItemId: "itm71770" }, Serialised: false, Quantity: 5 },
    { SerialisedEquipment: undefined, Type: { ItemId: "itm11025" }, Serialised: false, Quantity: 2 }];

...另一个代表实际使用过的设备列表。

var used = [
    { SerialisedEquipment: { SerialNo: "ser663033" }, Type: undefined, Serialised: true, Quantity: 1 },
    { SerialisedEquipment: { SerialNo: "ser288945" }, Type: undefined, Serialised: true, Quantity: 1 },
    { SerialisedEquipment: undefined, Type: { ItemId: "itm71770" }, Serialised: false, Quantity: 2 }];

我可以访问 underscore.js 并一直在尝试使用 _.groupBy 和 _.reduce 方法来尝试获得我想要的结果，但没有成功。我希望达到的结果是:

var result = [
    { SerialisedEquipment: { SerialNo: "ser663033" }, Type: undefined, Used: 1, Expected: 0, Remaining: 0 },
    { SerialisedEquipment: { SerialNo: "ser288945" }, Type: undefined, Used: 1, Expected: 1, Remaining: 0 },
    { SerialisedEquipment: { SerialNo: "ser855212" }, Type: undefined, Used: 0, Expected: 1, Remaining: 1 },
    { SerialisedEquipment: undefined, Type: { ItemId: "itm71770" }, Used: 2, Expected: 5, Remaining: 3 },
    { SerialisedEquipment: undefined, Type: { ItemId: "itm11025" }, Used: 0, Expected: 2, Remaining: 2 }];

我也一直在研究 underscore 提供的一些数组方法，但我不确定如何使用这些方法来指定合并的条件。有人对实现这一目标的最佳方法有任何建议吗？

更新

我已经设法获取两个数组的合并列表，删除重复项...

// Split based on the serialised flag - so I know to look at either the serialNo or Type property
var isSerialised = _.groupBy(required, function (equip) {
    return equip.Serialised;
});

// Get all the required serialised equipment that is not already in the used list
var serialised = _.filter(isSerialised[true], function (value) {
    return (!_.some(used, function (equip) {
        return equip.SerialisedEquipment && equip.SerialisedEquipment.SerialNo == value.SerialisedEquipment.SerialNo;
    }));
});

// Get all the required types that are not already in the used list
var types = _.filter(isSerialised[false], function (value) {
    return (!_.some(used, function (equip) {
        return equip.Type && equip.Type.ItemId == value.Type.ItemId;
    }));
});

// Combine the equipment that is not in the list with the equipment that is in the list
var result = _.union(used, serialised, types);

我认为现在只是循环遍历此结果列表与所需设备列表并根据序列号或类型总结匹配的设备的情况。

Answer 1

有时想要过多使用库会让您错过更简单的算法:

var resultsById = {};
function getTemporaryId(value) {
    return value.SerialisedEquipment ? value.SerialisedEquipment.SerialNo : value.Type.ItemId;
}
function getResultForValue(value) {
    var id = getTemporaryId(value);
    if(!resultsById[id]) {
        resultsById[id] = {
            SerialisedEquipment: value.SerialisedEquipment,
            Type: value.Type,
            Used: 0,
            Expected: 0,
            Remaining: 0
        };
    }
    return resultsById[id];
}
_.each(required, function(value) {
    var result = getResultForValue(value);
    result.Expected += value.Quantity;
    result.Remaining += value.Quantity;
});
_.each(used, function(value) {
    var result = getResultForValue(value);
    result.Used += value.Quantity;
    result.Remaining = Math.max(result.Remaining - value.Quantity, 0);
});

var merged = _.values(resultsById);

<小时/>

如果您确实想使用大量下划线，可以使用此解决方案:

var requiredValues = _.map(required, (function(value){
    //maybe want to clone value? value = _.clone(value);
    value.Used = 0;
    value.Expected = value.Quantity;
    return value;
}));
var usedValues = _.map(used, (function(value){
    //maybe want to clone value? value = _.clone(value);
    value.Used = value.Quantity;
    value.Expected = 0;
    return value;
}));
var mergedValues = _.chain(requiredValues.concat(usedValues))
    .groupBy(function(value){
        return value.SerialisedEquipment ? value.SerialisedEquipment.SerialNo : value.Type.ItemId;
    })
    .map(function(values) {
        var memo = {
            SerialisedEquipment: values[0].SerialisedEquipment,
            Type: values[0].Type,
            Used: 0,
            Expected: 0,
            Remaining: 0
        };
        return _.reduce(values, function(memo, value) {
            memo.Used += value.Used;
            memo.Expected += value.Expected;
            memo.Remaining = Math.max(memo.Expected - memo.Used, 0);
            return memo;
        }, memo)
    })
    .values()
    .value();