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As title. I shouldn't mutate state like this based on suggestion in Cannot see updates from child component through parent's callback (case array and push)

So, in https://codepen.io/jadecubes/pen/dygjGZL, I try to setWords(a new array), but it triggers infinite rendering.

// React.js libraries are added as external scripts in the JS settings of this pen

const { useState, useEffect } = React;

A = () => {
    const [info, setInfo] = useState("Hello world.");
    const [entered, setEntered] = useState('');
    return (
        <>
      <input type="text" 
        onChange={(e)=>{setInfo(e.target.value);}}
        onKeyUp={(e)=>{if(e.key=='Enter') setEntered(info); }}
        />
      <B enteredTxt={entered}/>
            <h1>{info}</h1>
        </>
    );
};

B = (props) => {
const [words,setWords] = useState([]);
  words.length=0;//I should not do this. I should re-assign a new array like setWords()
  words.push(props.enteredTxt);
  setWords(arrayGen());//But when I do this, the react infinite rendering happens!
  return(
      <div>
         {words} 
      </div>
  );
}

const arrayGen=()=>{
  return ['This ','is ','hello ', 'world!'];
}
const root = ReactDOM.createRoot(document.querySelector("#root"));
root.render(<A />);

Also, what's the suggested way to remove all items in an array? From Remove all the elements of the array in React JS , Maybe direct mutating is not a good idea? Any advice is welcome.

newArray = this.state.data.slice();
Yu Fang
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  • This post includes details. https://stackoverflow.com/questions/74034014/updating-state-to-the-same-state-directly-in-the-component-body/74036012#74036012 – Yu Fang May 14 '23 at 19:11

1 Answers1

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If you only want to call setWords only when enteredTxt changes, you should use useEffect like this:

useEffect(() => {
  setWords(arrayGen());
}, [props.enteredTxt])

To remove all items you can simply assign a new array:

newArray = [];

OneQ
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