How to find object in array and show it in React component?

Question

I have array of cities with objects like this:

[{id: 1, name: 'New York'}, {id: 2, name: 'London'} ...]

and I have a value of id.

I put elements (names) from array to select list. But I need to add first option with value from array (name) which have the corresponding id which I can't make it work.

My component:

const propTypes = {  
  cities: PropTypes.array,  
  enteredEvent: PropTypes.array  
};

class newEvent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      showInOption: ''
    };
    this.handleDictionary = this.handleDictionary.bind(this);
    this.searchTypeEvent = this.searchTypeEvent.bind(this);
  }

  componentDidMount() {
    this.searchTypeEvent();
  }

  handleDictionary(e) {
    ...
  }

  searchTypeEvent() {
    if (this.props.enteredEvent.cityid !== null && this.props.enteredEvent.cityid !== undefined) { // if I have id value
      const type = this.props.cities.find(el => el.id === this.props.enteredEvent.cityid); // find an object with id
      this.setState({ showInOption: type.name });
    }
    this.setState({ showInOption: 'Select something' });
  }

  render() {
    return (
      <div>       
        <select onChange={this.handleDictionary}>
          <option>{this.state.showInOption}</option> // here I need to add a value
          {this.props.cities.map(item => {   // here I call other options
            return (<InputSelect key={item.id} directory={item}/>);
          })}
        </select>        
      </div>
    );
  }
}

I have an error:

Uncaught TypeError: Cannot read property 'name' of undefined

How can I fix it?

You try to find an item by a search term by looking at the ids, is that intended? el.id === this.props.enteredEvent.cityname. You must also make sure that you actually find a type before trying to access name on it. — Tholle
– Tholle, Commented Nov 13, 2018 at 14:38
It's unknown what cityname. If it derives from an input, it's unlikely that it is a number that can pass === check. — Estus Flask
– Estus Flask, Commented Nov 13, 2018 at 14:39
@Tholle this.props.enteredEvent.cityid is correct. My mistake in post. I get object which I need (after find), but I can't get name value — Jack
– Jack, Commented Nov 13, 2018 at 14:51
@estus this.props.enteredEvent.cityid is correct. My mistake in post — Jack
– Jack, Commented Nov 13, 2018 at 14:51
Write console.log(type); right after the find and you will get undefined as the error says. I think it's a good idea to guard against the case when the cityid doesn't match a cities object id. — Tholle
– Tholle, Commented Nov 13, 2018 at 14:55

brk · Accepted Answer · 2018-11-13 14:41:22Z

6

It seems you need filter.It will return an array of object

let a = [{
  id: 1,
  name: 'New York'
}, {
  id: 2,
  name: 'London'
}]

function b(idToSearch) {
  return a.filter(item => {
    return item.id === idToSearch
  })
};

console.log(b(1))

answered Nov 13, 2018 at 14:41

brk

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1 Comment

Jack Over a year ago

I need to print name value. How can I do it?

Hemadri Dasari · Accepted Answer · 2018-11-13 15:06:02Z

4

Try this

  const type = Array.isArray(this.props.cities) && this.props.cities.find(el => el.id ==this.props.enteredEvent.cityid);
  this.setState({ showInOption: type ? type.name : null });

Make sure the name you enter matches with any one of the object in array

edited Nov 13, 2018 at 15:06

answered Nov 13, 2018 at 14:39

Hemadri Dasari

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3 Comments

Jack Over a year ago

When I call this function from option and in function I return value, this function called 6 times, and in last call I get the object value (I catch it, using console.log). Maybe React doesn't have time to perform this function?

Jack Over a year ago

no, it isn't help for my. I think there is asynchronous React problem

Andrew Irwin Over a year ago

Worked perfect for me ! thanks very much! Exactly what I wanted !! :)

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