How to find the highest value inside object by two item conditional?

Question

I'm trying to get the highest value of my object by ID and date. To explain better, this is my array:

[  
   {  
      "id":"6",
      "date":"201901",
      "value":"1"
   },
   {  
      "id":"6",
      "date":"201901",
      "value":"12"
   },
   {  
      "id":"6",
      "date":"201901",
      "value":"123"
   },
   {  
      "id":"6",
      "date":"201901",
      "value":"1231"
   },
   {  
      "id":"6",
      "date":"201902",
      "value":"4"
   },
   {  
      "id":"6",
      "date":"201902",
      "value":"45"
   },
   {  
      "id":"5",
      "date":"201902",
      "value":"56"
   },
   {  
      "id":"5",
      "date":"201902",
      "value":"46"
   }
]

I'm trying to get this return (Filtering the highest value by id and date):

[  
    {  
      "id":"6",
      "date":"201901",
      "value":"1231"
    },       
    {  
      "id":"6",
      "date":"201902",
      "value":"45"
    },
    {  
      "id":"5",
      "date":"201902",
      "value":"56"
    }       
]

In my code, I'm using map and filter but not works:

let resultados = array

array.map(item => {
  resultados.filter(itemFilter => {
    if(item.id == itemFilter.id && item.date == itemFilter.date){
      if(itemFilter.value > item.value){
        return itemFilter.value
      }
    }
  })
})

An similar solutis is this

Someone can help me?

Not sure if it's just me but, "_To explain better_..." - nope, still doesn't make sense. So you want to get the highest "value" for each "date" **for** each id? — Lewis, Apr 01 '19 at 15:15

Nina Scholz · Answer 1 · 2019-04-02T05:55:24.070

You could take a Map with a combined key of the wanted keys for grouping. Then take the greater value.

var data = [{ id: "6", date: "201901", value: "1" }, { id: "6", date: "201901", value: "12" }, { id: "6", date: "201901", value: "123" }, { id: "6", date: "201901", value: "1231" }, { id: "6", date: "201902", value: "4" }, { id: "6", date: "201902", value: "45" }, { id: "5", date: "201902", value: "56" }, { id: "5", date: "201902", value: "46" }],
    result = Array.from(data
            .reduce((m, o) => (key =>    
                !m.has(key) || m.get(key).value < o.value
                    ? m.set(key, o)
                    : m
            )(['id', 'date'].map(k => o[k]).join('|')), new Map)
            .values()
        );

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

I enjoyed your example, I saw that it works but a hand got a bit complicated for me, I'll look in the documentation item by item, thanks for the help! — Zkk, Apr 01 '19 at 22:30

Aaron · Accepted Answer · 2019-04-01T15:34:52.853

You can use Array.prototype.reduce :

yourArray.reduce( (accumulator, currentItem) => {
    var previouslyGreatestItem = accumulator.find(item => item.id == currentItem.id && item.date == currentItem.date);
    if (!previouslyGreatestItem) {
        accumulator.push(currentItem);
    } else if (previouslyGreatestItem.value < currentItem.value) {
        previouslyGreatestItem.value = currentItem.value;
    }
    return accumulator;
}, []);

var yourArray = [{"id":"6","date":"201901","value":"1"},{"id":"6","date":"201901","value":"12"},{"id":"6","date":"201901","value":"123"},{"id":"6","date":"201901","value":"1231"},{"id":"6","date":"201902","value":"4"},{"id":"6","date":"201902","value":"45"},{"id":"5","date":"201902","value":"56"},{"id":"5","date":"201902","value":"46"}];

var result = yourArray.reduce( (accumulator, currentItem) => {
 var previouslyGreatestItem = accumulator.find(item => item.id == currentItem.id && item.date == currentItem.date);
 if (!previouslyGreatestItem) {
  accumulator.push(currentItem);
 } else if (previouslyGreatestItem.value < currentItem.value) {
  previouslyGreatestItem.value = currentItem.value;
 }
 return accumulator;
}, []);

console.log(result);

Thank you so much! Good to know that in the logic of `if`, was in the way more or less certain — Zkk, Apr 01 '19 at 22:27

How to find the highest value inside object by two item conditional?

2 Answers2