Calculate sum of array one array attribute and constructing by key-CodePudding

I have an object

let returnObj = {
   test_on_Home_Page: {
     page: 'Home Page',
     total_sum: -141.16874354518953,
     top_url: null
   },
  test_on_Product_List: {
     page: 'Product List',
     total_sum: -147.16874354518953,
     top_url: null
   },
  testOther_on_Home_page: {
     page: 'Home Page',
     total_sum: -48.16874354518953,
     top_url: null
   },
}

I want to calculate total_sum of Object keys by pages, like this

 {
    HomePage : -189.33744
    ProductList : -147.168743
  }

I have tried

let totalCart = 0;

for(let errorName of Object.keys(returnObj)){
    if(returnObj[errorName]['page'] == "Cart"){
    totalCart  = returnObj[errorName]['total_sum'] 
    }
 }

But that doesn't look dynamic to me.

Can this be done with one line With something like this

 let list = [];
 
 for(let errorName of Object.keys(returnObj)){
    list[returnObj[errorName]]  = returnObj[errorName]['total_sum']
    
    }

CodePudding user response：

You need to iterate values, not keys:

let sums = {}

for (let obj of Object.values(returnObj))
    sums[obj.page] = (sums[obj.page] ?? 0)   obj.total_sum

CodePudding user response：

If you want to use more of a functional aproach

const sums = {}
Object.values(returnObj).forEach(item => {
  sums[item.page] = (sums[item.page] ?? 0)   item.total_sum
})

Using the lodash lib:

const sums = {}
_.values(returnObj).forEach(item => {
  sums[item.page] = (sums[item.page] ?? 0)   item.total_sum
})

CodePudding user response：

Here's an approach using Array.prototype.reduce on Object.values(returnObj):

const o = {
  test_on_Home_Page: {
    page: 'Home Page',
    total_sum: -141.16874354518953,
    top_url: null
  },
  test_on_Product_List: {
    page: 'Product List',
    total_sum: -147.16874354518953,
    top_url: null
  },
  testOther_on_Home_page: {
    page: 'Home Page',
    total_sum: -48.16874354518953,
    top_url: null
  },
}

const sums = Object.values(o)
  .reduce((a, { page: p, total_sum: s }) => ({...a, ...{ [p]: (a[p] ?? 0)   s } }), {});

console.log(sums);