查找具有多次匹配属性的JSON对象

Question

我需要找到具有相同名称属性的json数组中的每个元素,例如此处Alaska是两次,然后我需要比较两个对象的lastupdate并选择具有最新更新时间的对象.从stackoverflow中的答案中采用(抱歉,我丢失了链接)我可以删除具有相同名称属性的对象但是如何保留具有最新更新时间的对象？

[{
    "name": "Alaska",
    "Republican_fre": 3,
    "Democrats_fre": 0,
    "winner": "R",
    "iso_2": "AK",
    "electoral_vote": 3,
    "totalComponents": 3,
    "date": "29.06.2016",
    "lastupdate": "1467233426"
}, {
    "name": "Alabama",
    "Republican_fre": 3,
    "Democrats_fre": 0,
    "winner": "R",
    "iso_2": "AL",
    "electoral_vote": 9,
    "totalComponents": 3,
    "date": "29.06.2016",
    "lastupdate": "1467233426"
}, {
    "name": "Arkansas",
    "Republican_fre": 2,
    "Democrats_fre": 0,
    "winner": "R",
    "iso_2": "AR",
    "electoral_vote": 6,
    "totalComponents": 2,
    "date": "29.06.2016",
    "lastupdate": "1467233426"
},
{
    "name": "Alaska",
    "Republican_fre": 5,
    "Democrats_fre": 0,
    "winner": "R",
    "iso_2": "AK",
    "electoral_vote": 3,
    "totalComponents": 5,
    "date": "29.06.2016",
    "lastupdate": "1467282133"                 
}]

码:

function arrUnique(arr) {
    var cleaned = [];
    data.forEach(function(itm) {
        var unique = true;
        cleaned.forEach(function(itm2) {
         var minValue = Math.min(itm.lastupdate, itm2.lastupdate)
            if (_.isEqual(itm.name, itm2.name)){
            unique = false;
            } 
        });
        if (unique)  cleaned.push(itm);
    });
    return cleaned;
}

var uniqueStandards = arrUnique(data);

的jsfiddle:

预期输出 预期输出是它保持Alsaka对象之一具有最新的'lastupdate'值.因此,它首先检查具有相同名称属性的对象,然后比较lastupdate值并保持最新值

Answer 1

您可以使用下划线的sortBy()按其lastupdate键对reverse集合中的项目进行排序,reverse()使所有项目按lastupdate降序排序,然后使用uniq()仅保留唯一name项目.

var uniqueStandards = _.uniq(_.sortBy(data, 'lastupdate').reverse(), 'name');

var data = [{
  "name": "Alaska",
  "Republican_fre": 3,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AK",
  "electoral_vote": 3,
  "totalComponents": 3,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Alabama",
  "Republican_fre": 3,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AL",
  "electoral_vote": 9,
  "totalComponents": 3,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Arkansas",
  "Republican_fre": 2,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AR",
  "electoral_vote": 6,
  "totalComponents": 2,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Alaska",
  "Republican_fre": 5,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AK",
  "electoral_vote": 3,
  "totalComponents": 5,
  "date": "29.06.2016",
  "lastupdate": "1467282133"
}];

var uniqueStandards = _.uniq(_.sortBy(data, 'lastupdate').reverse(), 'name');

document.body.innerHTML = '<pre>' + JSON.stringify(uniqueStandards, 0, 4) + '</pre>';

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

一个vanilla JS解决方案将是:

var uniqueStandards = data
.slice() // this makes sure that we're not mutating the original array
.sort(function(x, y) { return y.lastupdate - x.lastupdate; }) // sort in descending order
.filter(function(x) {  // this ensure items with unique names
  return (this[x.name]? false: (this[x.name] = true));
}, {});

var data = [{
  "name": "Alaska",
  "Republican_fre": 3,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AK",
  "electoral_vote": 3,
  "totalComponents": 3,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Alabama",
  "Republican_fre": 3,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AL",
  "electoral_vote": 9,
  "totalComponents": 3,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Arkansas",
  "Republican_fre": 2,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AR",
  "electoral_vote": 6,
  "totalComponents": 2,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Alaska",
  "Republican_fre": 5,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AK",
  "electoral_vote": 3,
  "totalComponents": 5,
  "date": "29.06.2016",
  "lastupdate": "1467282133"
}];

var uniqueStandards = data
.slice() // this makes sure that we're not mutating the original array
.sort(function(x, y) { return y.lastupdate - x.lastupdate; }) // sort in descending order
.filter(function(x) {  // this ensure items with unique names
  return (this[x.name]? false: (this[x.name] = true));
}, {});

document.body.innerHTML = '<pre>' + JSON.stringify(uniqueStandards, 0, 4) + '</pre>';

或者,你可以试试lodash:

var uniqueStandards = _(data).orderBy('lastupdate', 'desc').uniqBy('name').value();

上面的snipet使用orderBy()按lastupdate降序排序集合,uniqBy()确保集合只有唯一的名称.

var data = [{
  "name": "Alaska",
  "Republican_fre": 3,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AK",
  "electoral_vote": 3,
  "totalComponents": 3,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Alabama",
  "Republican_fre": 3,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AL",
  "electoral_vote": 9,
  "totalComponents": 3,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Arkansas",
  "Republican_fre": 2,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AR",
  "electoral_vote": 6,
  "totalComponents": 2,
  "date": "29.06.2016",
  "lastupdate": "1467233426"
}, {
  "name": "Alaska",
  "Republican_fre": 5,
  "Democrats_fre": 0,
  "winner": "R",
  "iso_2": "AK",
  "electoral_vote": 3,
  "totalComponents": 5,
  "date": "29.06.2016",
  "lastupdate": "1467282133"
}];

var uniqueStandards = _(data).orderBy('lastupdate', 'desc').uniqBy('name').value();

document.body.innerHTML = '<pre>' + JSON.stringify(uniqueStandards, 0, 4) + '</pre>';

<script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.min.js"></script>