React map function fails with undefined property error during API data fetching

Other Questions API
1

Getting undefined error when trying to map through API response data

I’m working on a React app and keep running into an issue when fetching data from an external API. The map function throws an error saying it can’t read the property of undefined.

Here’s my component code:

import React, { Component } from "react";
import FilmCard from "./FilmCard";

const apiUrl = "http://www.omdbapi.com/?s=star&apikey=4ababda2";

class FilmCardList extends Component {
  constructor() {
    super();
    this.state = {
      films: []
    };
  }
  
  componentDidMount() {
    fetch(apiUrl)
      .then(response => response.json())
      .then(data => {
        this.setState({ films: data.Search || [] });
      })
      .catch(error => console.log("An error occurred: " + error));
  }

  render() {
    return (
      <div>
        {this.state.films.map(movie => (
          <FilmCard
            Title={movie.Title}
            Year={movie.Year}
            imdbID={movie.imdbID}
            Type={movie.Type}
          />
        ))}
      </div>
    );
  }
}

export default FilmCardList;

I’m still learning React so I’m not sure what’s causing this problem. Any help would be great!

2

Yeah, classic async issue! Your code looks fine, but OMDB sometimes returns weird responses. Add console.log(data) before setState to see what’s actually coming back. The API structure changes sometimes or returns null values that break the mapping. Also, you’re missing the key prop on FilmCard - React will throw warnings about that.

3

I’ve hit this same issue with async data in React. Your component renders before the API call finishes, so this.state.films starts as undefined. You’re already handling it with data.Search || [], but the API might return error responses without a Search property. Add a loading state - it’ll make things smoother. Set loading: true in your initial state, flip it to false when the fetch completes. Then just return a loading message when this.state.loading is true. Also add error handling. OMDB sometimes returns {“Response”:“False”,“Error”:“Movie not found!”} instead of the normal data structure, which will break your code.

4

The undefined error you’re encountering is likely due to the state not being populated at the moment of rendering. When the component mounts, the films array is initially empty, which can lead to issues if the API response takes time. To address this, consider implementing a conditional check in your render method to ensure films is an array before mapping through it. You can use: {Array.isArray(this.state.films) && this.state.films.map(movie => ())}. Furthermore, don’t forget to include a unique key prop for each FilmCard to enhance React’s rendering performance. Using the imdbID is a suitable choice for this key.