javascriptreactjsreact-hooksuse-state

Is it possible to use dynamic object keys in useState in Reactjs?


I'm trying to get the data from a form in which some fields are dynamic so that their names follow a pattern like the days of the week ending in 1 or 2.

In the onChange I send the name of the component that I am editing so the program knows what input is being edited but when I use the name that I send by parameter in the useState it does not detect it as the variable but as a normal string.

const [horas, setHoras] = useState({});  

const handleHoras = (e: any, nomb: string) => {
        setHoras({
            ...horas,
            nomb: e.target.value
        })
    }

I've tried to declare the state as an array (as I show below) but the variable is not overwriting itself but adding variables with the same name every time the value changes.


    const handleHoras = (e: any, nomb: any) => {
        setHoras(
            [
                ...horas,
                { 'name': nomb, 'value': e.target.value }
            ]
        )
    }


Solution

  • Use the target prop of the callback function to get name and value, and do not forget to add [ ] around the name to make it dynamic.

    // import { useState } from 'react' --> with babel import
    const { useState } = React  // --> with inline script tag
    
    const App = () => {
      const [inputValues, setInputValues] = useState({})
    
      const handleChange = ({ target }) => {
    
        setInputValues(prevInputValues => ({
          ...prevInputValues,
          [target.id]: target.value
        }))
      }
      
      console.log('state:', inputValues)
    
      return (
        <form>
          <input id="foo" onChange={handleChange} />
          <input id="bar" onChange={handleChange} />
        </form>
      )
    }
      
    ReactDOM.render(<App />, document.getElementById('root'))
    <script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.9.0/umd/react.production.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.9.0/umd/react-dom.production.min.js"></script>
    <div id="root"></div>