Group by and sum

Directions

Group by objects in an array and get the sum of the group

Examples:

Input:

  [ 
    { Phase: 'Phase 1', Step: 'Step 1', Task: 'Task 1', Value: '5' },
    { Phase: 'Phase 2', Step: 'Step 2', Task: 'Task 1', Value: '35' },
    { Phase: 'Phase 1', Step: 'Step 2', Task: 'Task 1', Value: '15' },
    { Phase: 'Phase 1', Step: 'Step 2', Task: 'Task 2', Value: '20' },
    { Phase: 'Phase 2', Step: 'Step 1', Task: 'Task 1', Value: '25' },
    { Phase: 'Phase 2', Step: 'Step 2', Task: 'Task 2', Value: '40' },
    { Phase: 'Phase 2', Step: 'Step 1', Task: 'Task 2', Value: '30' },
    { Phase: 'Phase 1', Step: 'Step 1', Task: 'Task 2', Value: '10' }
  ]

Output:

  [
    { Phase: "Phase 1", Value: 50 },
    { Phase: "Phase 2", Value: 130 }
  ]

Solutions

• Solution #1

  const groupBy = (data, key) => {
    return data.reduce((storage, item) => {
      // get the first instance of the key by which we're grouping
      const group = item[key];
  
      // set `storage` for this instance of group to the outer scope (if not empty) or initialize it
      storage[group] = storage[group] || [];
  
      // add this item to its group within `storage
      storage[group].push(item);
  
      // return the updated storage to the reduce function, which will then loop through the next
      return storage;
    }, {}); // {} is the initial value of the storage
  };
  

  ---

  const res = groupBy(dataArr, 'Phase');
  console.log(res);
  

  ---

  Result:

    {
      'Phase 1': [
        { Phase: 'Phase 1', Step: 'Step 1', Task: 'Task 1', Value: '5' },
        { Phase: 'Phase 1', Step: 'Step 2', Task: 'Task 1', Value: '15' },
        { Phase: 'Phase 1', Step: 'Step 2', Task: 'Task 2', Value: '20' },
        { Phase: 'Phase 1', Step: 'Step 1', Task: 'Task 2', Value: '10' }
      ],
      'Phase 2': [
        { Phase: 'Phase 2', Step: 'Step 2', Task: 'Task 1', Value: '35' },
        { Phase: 'Phase 2', Step: 'Step 1', Task: 'Task 1', Value: '25' },
        { Phase: 'Phase 2', Step: 'Step 2', Task: 'Task 2', Value: '40' },
        { Phase: 'Phase 2', Step: 'Step 1', Task: 'Task 2', Value: '30' }
      ]
    }  
  

  ---

  ---

  const getSumPerGroup = (data, key) => {
    const result = [];
    Object.keys(data).forEach((currObjKey) => {
      result.push({
        'Phase': currObjKey,
        'Value': data[currObjKey].reduce((acc, item) => {
          return acc + parseInt(item[key]);
        }, 0)
      });
    });
    return result;
  };
  

  ---

  const res1 = getSumPerGroup(res, 'Value');
  console.log(res1);  
  

  ---

  Result:

    [ 
      { Phase: 'Phase 1', Value: 50 }, 
      { Phase: 'Phase 2', Value: 130 } 
    ]
  

  ---

  //gist.github.com/robmathers/1830ce09695f759bf2c4df15c29dd22d