React Native iterate through array objects and cacluate sum up value

Question

I am writing a piece of function in my React Native App, I have called an api, and it turns me this json array with objects, and stored in this.props.data:

           [{name:'Jhon', income:28, spending:20},
            {name:'Anna', income:82, spending:50},
            {name:'Peter', income:141, spending:70}
           ]

I wish to iterate throught this array object and sum up the income and spending value, eventually to generate out a new object (everyone) and appened to original this.props.data and make something looks like below:

           [{name:'Jhon', income:28, spending:20},
            {name:'Anna', income:82, spending:50},
            {name:'Peter', income:141, spending:70},
            {name:'Everyone', income:251, spending:140}
           ]

My current attempt is below, but doesn't really work, please advise with code example, thanks

const CustomListview = ({ itemList }) => (
    var everyoneObject = {
      name: 'everyone',
      income: 0,
      spending: 0
    }

    itemList.map(({name, income, spending}) => { 
        everyoneObject = {
          name: 'everyone',
          income: income++,
          spending: spending++
        }
    })

    itemList.push(everyoneObject);

    <View style={styles.container}>
        <FlatList
            data={itemList}
            renderItem={({ item }) =>
              <TillReportRow
                  name={item.name}
                  income={item.income}
                  spending={item.spending}
              />}
            keyExtractor={(item, index) => index.toString()}
        />
    </View>
);

senthilbalaji · Accepted Answer · 2018-12-15 13:13:39Z

1

you have almost come near to correct logic,

this can be one way you achieve this,

 let everyOneObj = { name:'Everyone', income: 0, spending: 0 };

 itemList.forEach((item) => { `
      everyOneObj.income += item.income;
      everyOneObj.spending += item.spending;
 });

 itemList.push(everyOneObj);

answered Dec 15, 2018 at 13:13

senthilbalaji

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Comments

Eugene · Accepted Answer · 2018-12-15 13:10:30Z

0

You need to use reduce to create a single new object, not map

const itemList = [
  { name: "Jhon", income: 28, spending: 20 },
  { name: "Anna", income: 82, spending: 50 },
  { name: "Peter", income: 141, spending: 70 }
];

const everyone = itemList.reduce(
  (acc, { income, spending }) => {
    acc.income += income;
    acc.spending += spending;
    return acc;
  },
  { name: "everyone", income: 0, spending: 0 }
);

itemList.push(everyone);
console.log(itemList);

which prints

[
  { name: "Jhon", income: 28, spending: 20 },
  { name: "Anna", income: 82, spending: 50 },
  { name: "Peter", income: 141, spending: 70 },
  { name: "everyone", income: 251, spending: 140 }
]

answered Dec 15, 2018 at 13:10

Eugene

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