import React, {useState} from ' React ';
导出默认功能TextForm(props){
const [text,setText]=useState();
const toUppercase=()=>{
console.log("button is clicked");
let newText=text.toUpperCase();
setText(newText);
}
const changingText=(event)=>{
setText(event.target.value)
}
return(
<>
<div className="container">
<h1>{props.heading}</h1>
<div className="mb-3">
<textarea className="form-control" id="txtarea" rows="10" value={text} placeholder="Enter Your text here" onChange={changingText}></textarea>
</div>
<button className="btn btn-primary" onClick={toUppercase}>Click to convert to uppercase</button>
</div>
<div className="container my-2">
<h1>Your text summary</h1>
<p>{text.length} is number of character</p>
</div>
</>
)
}
显示的错误如下[1]:https://i.stack.imgur.com/MeoMH.jpg
这是你的错误
setText(...text,event.target.value);
首先存储前一个值并添加新值,否则settext
每次被一个单词覆盖