How to iterate through an array of objects from json in React.js

Question

I am trying to loop through an array of objects in an external json file using the map function. The loop succeeds but I am not sure how to access the object properties. See below.

I am using object.keys(obj).map() but cannot get access to the individual properties. Map keeps outputting the array index numbers.

This is my data I want to iterate through.

[
   {
     "id" : "12345",
     "customer" : "BMW",
   },
   {
     "id" : "45678",
     "customer" : "Ford",
   },
   {
     "id" : "78901",
     "customer" : "Google",
   } 
]

I have a state hook that the data will be saved to

const [accountData, setAccountData] = useState('');

The function below gets the data from the external json file and sets the state with it.


 axios.get('./data/account-info.json')
  .then((response) => {
     //set state
     setAccountData(response.data);
  })
  .catch((error) => {
     console.log(error);
  });

I iterate through the state object with a map function

Object.keys(accountData).map((id,customer) => {
  return(
    <div>
      <p>ID: {id}</p>
      <p>Name: {customer}</p>
    </div>
  )
})

The output keeps printing out the index numbers instead of the appropriate values

//outputted elements

<div>
  <p>ID: 0</p>
  <p>Name: 0</p>
</div>

<div>
  <p>ID: 1</p>
  <p>Name: 1</p>
</div>

<div>
  <p>ID: 2</p>
  <p>Name: 2</p>
</div>

Can you please tell me what I am doing wrong here? I know it has to be something simple.

dance2die · Accepted Answer · 2019-08-07 15:25:55Z

3

You can iterate accountData directly, as it's an array.
Each item will be an object, so you need to destructure as you see below.
(you don't need to but that's was the intention I perceived from your code)

And also you need to add a key to each element, to notify React how to keep track of elements.

//               👇 destrcuture the properties
accountData.map(({ id,customer }) => {
  return(
   {/* 👇 make sure to add keys here too */}
    <div key={id}>
      <p>ID: {id}</p>
      <p>Name: {customer}</p>
    </div>
  )
})

-- Reply to the [COMMENT] --

so whenever I remove the object.keys() it throws this error at me TypeError: accountData.map is not a function

Would you double check if response.data is as what you mentioned in the post?
If you run the code below, it will correctly print id & customer array.

let accountData = [
   {
     "id" : "12345",
     "customer" : "BMW",
   },
   {
     "id" : "45678",
     "customer" : "Ford",
   },
   {
     "id" : "78901",
     "customer" : "Google",
   } 
] 
accountData.map(({id, customer}) => console.log(id, customer))

edited Aug 7, 2019 at 15:25

answered Aug 6, 2019 at 20:09

dance2die

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2 Comments

David Sanders Over a year ago

so whenever I remove the object.keys() it throws this error at me TypeError: accountData.map is not a function

dance2die Over a year ago

@DavidSanders I've updated the answer. accountData.map should work, if the data you mentioned in the question is what is being returned

jose alejandro sanchez mariño · Accepted Answer · 2019-08-06 20:07:07Z

2

try this

Object.keys(accountData).map((e) => { return(

ID: {e.id}

Name: {e.customer}

) })

answered Aug 6, 2019 at 20:07

jose alejandro sanchez mariño

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Comments

Matt Aft · Accepted Answer · 2019-08-06 20:05:07Z

0

Object.keys(accountData) will give you the keys of the array, ex 0,1,2. just do accountData.map to iterate through the array instead.

answered Aug 6, 2019 at 20:05

Matt Aft

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Comments

Jackkobec · Accepted Answer · 2019-08-06 20:09:51Z

0

accountData.map(customer => {
  return(
    <div
      key={ customer.id }
     >
      <p>ID: { customer.id }</p>
      <p>Name: { customer.customer }</p>
    </div>
  )
})

edited Aug 6, 2019 at 20:09

answered Aug 6, 2019 at 20:05

Jackkobec

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2 Comments

Michael Abeln Over a year ago

Just keep in mind that using the index of a map function to define the key is an anti-pattern in react. reactjs.org/docs/lists-and-keys.html

Jackkobec Over a year ago

Right you are. Suppose that id is unique. Code has been refactored.

TopW3 · Accepted Answer · 2019-08-07 06:10:03Z

0

Object.keys function returns the array of its keys. For array object, its keys are its indices. So in case of your accountData, Object.keys(accountData) returns [ '0', '1', '2' ].

If you still want to use Object.keys function, you can do like this.

Object.keys(accountData).map(key => (
    <div key={accountData[key].id}>
        <p>ID: {accountData[key].id}</p>
        <p>Name: {accountData[key].customer}</p>
    </div>
));

But in case of an array, it would be better to apply map function directly to it.

accountData.map(account => (
    <div key={account.id}>
        <p>ID: {account.id}</p>
        <p>Name: {account.customer}</p>
    </div>
));

That's all.

answered Aug 7, 2019 at 6:10

TopW3

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