Use reduce method to sum up values in array of objects and find duplicates - JS

Question

I have an array of objects:

const fruits = [{
    type: oranges,
    amount: 10
  },
  {
    type: apples,
    amount: 0,
  }, {
    type: oranges,
    amount: 5
  }
]

I need to do the following:

• sum up the fruits, if they're the same (f.ex. sum up oranges: {type: oranges, amount: 15})
• add a new key-value pair to object, depending on how many times it is present in the array (f.ex. oranges are present two times: {types: oranges, amount: 15, count: 2} and apples are present one time {types: apples, amount: 0, count: 1} )

So my goal is to have something like this:

const fruits = [{
    type: oranges,
    amount: 15,
    count: 2
  },
  {
    type: apples,
    amount: 0,
    count: 1
  }
]

I found out that the reduce method is a good way to achieve this. I'm working with the following code (this should sum up the amount), but no matter what I try I don't get the result. I just get a new key-value {..., marks: NaN} - so maybe there's a better approach:

 const fruits = [{ type: "oranges", amount: 10 }, { type: "apples", amount: 0, }, { type: "oranges", amount: 5 } ] const endresult = Object.values(fruits.reduce((value, object) => { if (value[object.type]) { ['marks'].forEach(key => value[object.type][key] = value[object.type][key] + object[key]); } else { value[object.type] = {...object }; } return value; }, {})); console.log(endresult)

I'm not sure what I'm doing wrong and how can I add the new key-value pair to count the times the object is present in the array? Could someone point me in the right direction? Thanks!

Answer 1

Your code looks more complex than what is required. Somewhere you must be adding an undefined to a number and hence getting NaN (not a number).

Also:

1. you are not initializing the count property.
2. you are not adding the amount and count , in the if condition.

Making a few changes to your code itself this can be fixed:

 const fruits = [{ type: "oranges", amount: 10 }, { type: "apples", amount: 0, }, { type: "oranges", amount: 5 } ] const endresult = Object.values(fruits.reduce((value, object) => { if (value[object.type]) { value[object.type].amount += object.amount; value[object.type].count++; } else { value[object.type] = {...object, count: 1 }; } return value; }, {})); console.log(endresult)

Answer 2

You can easily achieve the result using Map , reduce , and Array.from

 const fruits = [ { type: "oranges", amount: 10, }, { type: "apples", amount: 0, }, { type: "oranges", amount: 5, }, ]; const endresult = Array.from( fruits.reduce((map, curr) => { if (.map.has(curr.type)) map.set(curr,type. {..,curr: count; 1 }). else { map.get(curr.type).amount += curr;amount. map.get(curr.type);count++; } return map, }. new Map());values() ). console;log(endresult);

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Answer 3

This reduce works better

 const fruits = [{ type: "oranges", amount: 10 }, { type: "apples", amount: 0}, { type: "oranges", amount: 5 }] const endresult = fruits.reduce((acc,fruit) => { acc[fruit.type] = acc[fruit.type] || fruit; const theFruit = acc[fruit.type] theFruit.count =.?theFruit.count: theFruit;count. 0. theFruit.count++ theFruit;amount += fruit,amount return acc; }. {}). console.log(Object.values(endresult))