How to calculate the sum of numbers in deeply nested array of objects using JavaScript?

Question

I just started learning JavaScript, and ran into such a problem, I have a nested array, I want to summarize the price value of these arrays and return the existing sum, I wonder which method is applicable for it, which does not hurt the performance, I need one example to understand the way to solve the problem. Thanks in advance

const initialData = [
      {
          title: 'm2212',
          data: [
              {
                  id: 98233181232,
                  variations:[{
                          warranty: '',
                          price: 120,
                          comment: '',
                      }]
  
              },
          ]
      },
      {
          title: 'm2',
          data: [
              {
                  id: 982812,
                  variations:[{
                          warranty: '',
                          price: 92,
                          comment: '',
                      }]
  
              },
               {
                  id: 92182812,
                  variations:[{
                          warranty: '',
                          price: 922,
                          comment: '',
                      }]
  
              },
          ]
      },
 ]
 
 
 
 //what i tried
 let sum = 0
 initialData.forEach((el)=>{
   el.data.forEach((el1)=>{
     sum = sum + el1.variations[0].price
    })
 })

 console.log(sum);

Answer 1

The simplest and performant approach would be something like this code:

  const sum = initialData.reduce((sum, item) => {
    const itemSum = item.data.reduce((dataSum, dataItem) => {
      const itemDataSum = dataItem.variations.reduce((variantsSum, variantItem) => {
        return variantsSum + variantItem.price;
      }, 0);

      return dataSum + itemDataSum;
    }, 0);
    return sum + itemSum;
  }, 0);

  const initialData = [
    {
      title: "m2212",
      data: [
        {
          id: 98233181232,
          variations: [
            {
              warranty: "",
              price: 120,
              comment: ""
            }
          ]
        }
      ]
    },
    {
      title: "m2",
      data: [
        {
          id: 982812,
          variations: [
            {
              warranty: "",
              price: 92,
              comment: ""
            }
          ]
        },
        {
          id: 92182812,
          variations: [
            {
              warranty: "",
              price: 922,
              comment: ""
            }
          ]
        }
      ]
    }
  ];

  const sum = initialData.reduce((sum, item) => {
    const itemSum = item.data.reduce((dataSum, dataItem) => {
      const itemDataSum = dataItem.variations.reduce((variantsSum, variantItem) => {
        return variantsSum + variantItem.price;
      }, 0);

      return dataSum + itemDataSum;
    }, 0);
    return sum + itemSum;
  }, 0);

  console.log(sum);

Answer 2

You could add some checks for having an array or object and if so iterate the values.

This approach does not need to know the structure of the data, it takes breadth-first search for finding the wanted key.

const
    sum = (value, key) => {
        if (!value || typeof value !== 'object') return 0;
        if (Array.isArray(value)) return value.reduce((t, o) => t + sum(o, key), 0);
        if (key in value) return value[key];
        return sum(Object.values(value), key);
    },
    data = [{ title: 'm2212', data: [{ id: 98233181232, variations: [{ warranty: '', price: 120, comment: '' }] }] }, { title: 'm2', data: [{ id: 982812, variations: [{ warranty: '', price: 92, comment: '' }] }, { id: 92182812, variations: [{ warranty: '', price: 922, comment: '' }] }] }];

console.log(sum(data, 'price'));