Calculate sum of multiple values in array of objects

Question

I have an array of objects like below, where I want to calculate the sum of job_security, skill_development and company_culture these fields.

reviews = [
  {
      id: 1,
      job_security: '2.0',
      skill_development: '3.0',
      company_culture: '4.0',
      is_anonymous: false,
      pros: 'Test 1...',
      cons: "Test 1...",
      created_at: '2022-10-19T19:07:18.000Z',
  },
  {
      id: 2,
      job_security: '3.0',
      skill_development: '1.0',
      company_culture: '2.0',
      is_anonymous: false,
      pros: 'Test 2...',
      cons: "Test 2...",
      created_at: '2022-10-19T19:07:25.000Z',
  },
  {
      id: 3,
      job_security: '4.0',
      skill_development: '1.0',
      company_culture: '2.0',
      is_anonymous: false,
      pros: 'Test 3...',
      cons: "Test 3...",
      created_at: '2022-10-19T19:07:35.000Z',
  }
]

I am expecting an output like this, where total sums of all the fields will return as an object

{
   job_security: '4.0',
   skill_development: '6.0',
   company_culture: '7.0',
}

This is what I have done :

const filteredKeys = [
  'job_security'
  'company_culture',
  'skill_development',
];

reviews.forEach((review: any) => {
   Object.keys(review).reduce(
      (accu: any, key: string) => {
         if (filteredKeys.includes(key)) {
            const rating = Number(review[key]);
            accu[key] = accu[key] || rating;
            accu[key] += rating;
         }
         return accu;
      },
      Object.create(null)
   );
});

It's not clear to me what you want. The sum of the fields you named in each of the three example objects of the top array are: 9, 6, 7 for elements 0, 1, and 2 respectively of the array of objects. But you show an expected output consisting of an object containing the three named properties and their values (which seem unrelated to the example array), and no sum. Could you show the exact output you need from the example array given? — Dave Pritlove
– Dave Pritlove, Commented Nov 7, 2022 at 2:31
The arithmetic in your example result is inconsistent with the example inputs. 2.0 + 3.0 + 4.0 ≠ 4.0, 3.0 + 1.0 + 1.0 ≠ 6.0, 4.0 + 2.0 + 2.0 ≠ 7.0 I hope people will still get the idea that it's supposed to be the sum. I'm just saying the question would be better if it used the correct sums. People who are into programming are often quite particular about numerical details and consistency. Many of us have made a career of it. — Wyck
– Wyck, Commented Nov 7, 2022 at 3:22

Mister Jojo · Accepted Answer · 2022-11-07 03:32:02Z

3

simply use Array.reduce() method :

const reviews = [{id: 1,job_security: '2.0',skill_development: '3.0',company_culture: '4.0',is_anonymous: false,pros: 'Test 1...',cons: "Test 1...",created_at: '2022-10-19T19:07:18.000Z',},{id: 2,job_security: '3.0',skill_development: '1.0',company_culture: '2.0',is_anonymous: false,pros: 'Test 2...',cons: "Test 2...",created_at: '2022-10-19T19:07:25.000Z',},{id: 3,job_security: '4.0',skill_development: '1.0',company_culture: '2.0',is_anonymous: false,pros: 'Test 3...',cons: "Test 3...",created_at: '2022-10-19T19:07:35.000Z',}];

const sums = reviews.reduce( (s,e,i,{[i+1]:eNext})=>
  {
  Object.keys(s).forEach( k => s[k] += +e[k] );
  if (!eNext) // for the last (no next element), change values to string
    Object.keys(s).forEach( k => s[k] = s[k].toFixed(1) );
  return s
  }
  ,{ job_security: 0, skill_development: 0, company_culture: 0 });
  
  
console.log( sums )

edited Nov 7, 2022 at 3:32

answered Nov 7, 2022 at 2:45

Mister Jojo

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2 Comments

RAHUL KUNDU Over a year ago

Is there any way to make keys (s.job_security) dynamic?

Mister Jojo Over a year ago

@RAHULKUNDU I have changed my answer for more "dynamic" ...

HappyDev · Accepted Answer · 2022-11-07 02:33:10Z

You could do something like this

const reviews = [
  {
      id: 1,
      job_security: '2.0',
      skill_development: '3.0',
      company_culture: '4.0',
      is_anonymous: false,
      pros: 'Test 1...',
      cons: "Test 1...",
      created_at: '2022-10-19T19:07:18.000Z',
  },
  {
      id: 2,
      job_security: '3.0',
      skill_development: '1.0',
      company_culture: '2.0',
      is_anonymous: false,
      pros: 'Test 2...',
      cons: "Test 2...",
      created_at: '2022-10-19T19:07:25.000Z',
  },
  {
      id: 3,
      job_security: '4.0',
      skill_development: '1.0',
      company_culture: '2.0',
      is_anonymous: false,
      pros: 'Test 3...',
      cons: "Test 3...",
      created_at: '2022-10-19T19:07:35.000Z',
  }
]

const filters =  [
  'job_security',
  'company_culture',
  'skill_development',
];
const output = reviews.reduce((acc, next)=> {
  for (let filter of filters){
      if (!(filter in next)) throw new Error(`Cannot find ${filter} in object`)
      if (!(filter in acc)) acc[filter] = 0;
      acc[filter]+= +next[filter];
  }
  return acc;
}, {})

flyingfox · Accepted Answer · 2022-11-07 02:35:16Z

You can use reduce() to do it

let reviews = [
  {
      id: 1,
      job_security: '2.0',
      skill_development: '3.0',
      company_culture: '4.0',
      is_anonymous: false,
      pros: 'Test 1...',
      cons: "Test 1...",
      created_at: '2022-10-19T19:07:18.000Z',
  },
  {
      id: 2,
      job_security: '3.0',
      skill_development: '1.0',
      company_culture: '2.0',
      is_anonymous: false,
      pros: 'Test 2...',
      cons: "Test 2...",
      created_at: '2022-10-19T19:07:25.000Z',
  },
  {
      id: 3,
      job_security: '4.0',
      skill_development: '1.0',
      company_culture: '2.0',
      is_anonymous: false,
      pros: 'Test 3...',
      cons: "Test 3...",
      created_at: '2022-10-19T19:07:35.000Z',
  }
]

let keys =  [
  'job_security',
  'company_culture',
  'skill_development',
];
let result = reviews.reduce((a,v) =>{
  keys.forEach(k =>{
    a[k] = (a[k]??0) + (+v[k]) 
   })
  return a
},{})
console.log(result)

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