Question

我有一个简单的代码，试图使用Scanner scanner=new Scanner(System.in); System.out.println("Enter test 1 value"); // initial value is created and passed in to test method here double test1 = Double.parseDouble(scanner.nextLine()); // here we grab the return value of the test method double value1 = test(test1); System.out.println("Enter test 2 value"); // initial value is created and passed in to tests method here double test2 = Double.parseDouble(scanner.nextLine()); // here we grab the return value of the tests method. double value2 = tests(test2); // pass in the value returned from both methods (ensuring we have the latest user input) to display display(value1, value2);替换旧内容，并使用新内容创建新元素。

例如

replace prototype

class App extends React.Component {
constructor() {
    super();
    this.state = {
      name: 'bold'
    };
  }
  replace = () =>{
    let oldState = this.state.name;
    oldState = oldState.replace(/bold/i, React.createElement('b',{ children: 'withBold'}) )
    console.log(oldState)
    this.setState({ name: oldState})
  }
  render() {
    return (
      <div>
      <button onClick={this.replace}>Click</button><br />
       {this.state.name}
      </div>
    );
  }
}

ReactDOM.render(<App />, document.getElementById('code'));

我已经尝试<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='code'></div>我得到了document.createElement

我的代码有什么问题？

Answer 1

String.prototype.replace期望替换值是字符串或函数。您正在传递一个对象（React.createElement(...)）。

您的问题在这里：

oldState = oldState.replace(
    /bold/i,
    // The following must be a string, but you are passing in an object:
    React.createElement('b',{ children: 'withBold'})
);

有很多方法可以解决此问题。就个人而言，对于这样一个简单的案例，我会写：

this.setState(prevState => ({
    name: prevState.name.toLowerCase() === 'bold'
        ? <b>withBold</b>
        : prevState.name
});

反应createElement不工作返回[对象对象]

1 个答案: