Manage State Locally First Map not a Function

JavaScript
1

Tell us what’s happening:

// running test
this.state.messages.map is not a function
this.state.messages.map is not a function
// tests completed

Your code so far


class DisplayMessages extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      input: '',
      messages: []
    }

    this.handleChange = this.handleChange.bind(this)
    this.submitMessage = this.submitMessage.bind(this)
  }
  // add handleChange() and submitMessage() methods here
  handleChange(e){
    this.setState({
      input: e.target.value,
    });
  }

  submitMessage(e){
    this.setState({
      input: '',
      messages: this.state.messages.push(this.state.input)
    });
  }
  render() {
    const messages = this.state.messages.map(function(message){
      return <li> {message} </li>}
    );
    return (
      <div>
        <h2>Type in a new Message:</h2>
        <input
          type='text' 
          onChange={this.handleChange} 
          value={this.state.input} />
        <button onClick={this.submitMessage}> 
          Add Message
        </button>
        <ul>
          {messages}
        </ul>

      </div>
    );
  }
};

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36.

Link to the challenge:
https://learn.freecodecamp.org/front-end-libraries/react-and-redux/manage-state-locally-first

2

Array.prototype.push does not return the array as you’re expecting, but the length of the array after pushing the element. You’ll have to refactor submitMessage.

3

Thanks, .concat did the trick. But i think is not the right way to do it, cuz .concat modifies the original array , so is redundant. Any Better way?

Regards.

4

It doesn’t, though. Array.prototype.concat returns a new array, which is how it works in your code. I wouldn’t worry about optimizing this any further, just move on to bigger problems.

5

Thanks for pointing out the return value using the Array.prototype.push method. I was having the same issue, but reading this resolved it for me. I refactored using the spread operator.