我正在尝试使用 React 中的 usestate 将元素添加到 object？

Question

I am trying to add a new fields in the useState hook

// prevstate  
let [currentdata, setcurrentdata] = useState({
   id:'',
   name:''
  })

I try to add new fields in the object like that

   setcurrentdata(currentdata => ({
            ...currentdata,
            q: quantity,
          }))

but it did not add new fields

Answer 1

The code snippet below may be one possible solution to achieve the desired objective.

NOTE: I personally dislike the idea of using useState in conjunction with such objects & prefer multiple simpler useState on each variable instead.

Code Snippet

 const {useState} = React; const MyFunction = () => { const [badStateObj, setBadStateObj] = useState({ id: '', name: '' }); const clickHandler = (propName) => setBadStateObj(prev => ({...prev, [propName]: prev[propName] || '' })); const updateHandler = (propName, propVal) => setBadStateObj(prev => ({...prev, [propName]: propVal })); return ( <div> {Object.entries(badStateObj).map(([k,v]) => ( <div> Key: {k} &emsp; Value: {v} &emsp; &emsp; <button onClick={() => updateHandler(k, prompt( `Enter new value for ${k}` ))} > Update {k} </button> </div> ))} <button onClick={() => clickHandler(prompt('Enter prop name'))} > Add new prop </button> </div> ); }; ReactDOM.render( <div> <h4>Demo showing the useState that I personally dislike</h4> <MyFunction /> </div>, document.getElementById("react") );

 <div id="react"></div> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.1/umd/react.production.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.1/umd/react-dom.production.min.js"></script>

Explanation

• The badStateObj is initialized with only id and name props
• When user clicks the Add new prop button, a new prop may be added
• Separate buttons exist to update the value of each individual prop
• clickHandler adds the new prop entered by user with '' value.
• updateHandler accepts propName and propVal as parameters and updates the appropriate props within the badStateObj .