setState() of specific array item

Question

I'm generating multiple inputs and want to bind their values to array stored in state. I'm using an array because the number of inputs varies and I can't create them statically. I'm assigning their value and it works as expected:

    this.setState({
      wordInputs: this.state.userTitle.map((word) => {
      let input = <input type="text" key={i} value={this.state.userTitle[i]} onChange={this.checkWordInput}/>
      i++
      return input
      })
    })

Now I want to handle user input with checkWordInput() and here comes my question: how do I access input's key property set earlier in order to update the this.state.userTitle array? Or is there a different way to do this?

I'd suggest storing the metadata in state, and then using that to generate the components in render(), as oppose to storing components in state. — lux
– lux, Commented Jan 2, 2017 at 20:13
@lux Thanks, I'll do that, I'm new to React. But I don't see how it solves me issue. Or did you just give me an advice? — Chris Kraszewski
– Chris Kraszewski, Commented Jan 2, 2017 at 20:18
As a best practice... jsx should be written inside the render method. — Khalid Azam
– Khalid Azam, Commented Jan 3, 2017 at 7:13

Oleksandr T. · Accepted Answer · 2017-01-02 20:32:27Z

2

I think you don't need store inputs in state, you can move inputs to render, like so

class App extends React.Component {
  constructor() {
    super();
    this.state = {
      userTitle: [
        'title - 1',
        'title - 2',
        'title - 3',
        'title - 4'
      ]
    };
    
  }
  
  checkWordInput(index, e) {
    this.setState({
      userTitle: this.state.userTitle.map((title, i) => (
        i === index ? e.target.value : title
      ))
    })  
  }
        
  render() {
    const inputs = this.state.userTitle.map((title, index) => ( 
      <input 
        type="text" 
         key={index} 
         value={title} 
         onChange={ (e) => this.checkWordInput(index, e) }
      />
    ));
        
    return (
      <form>
        { inputs }

        { this.state.userTitle.map((title, i) => <p key={i}> { title }</p>) }
      </form>
    );
  }          
}
        
ReactDOM.render(
  <App />, 
  document.getElementById('app')
);

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>

edited Jan 2, 2017 at 20:32

answered Jan 2, 2017 at 20:24

Oleksandr T.

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1 Comment

Chris Kraszewski Over a year ago

Thanks! That's exactly what I wanted, didn't think of passing index to onChange function.

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