onClick不起作用， <button>但可以起作用</button>

Question

trying to trigger an event onClick, it works when i use "a" tag but when i use button it doesn't :

constructor(props) {
    super(props);
    this.backwardWeek = this.backwardWeek.bind(this);

    this.state = {
      displayedWeek: 0,
      inputs: []

    }; 
backwardWeek() {
    this.state.displayedWeek = this.state.displayedWeek - 1;   
   }

render(){

return (   
  <button onClick={this.backwardWeek}>  <span className="glyphicon glyphicon- 
   arrow-left" /></button> 
  );
    }

Answer 1

当您必须更新组件的状态时，react组件具有方法setState（），您可以使用该方法进行更新。

Answer 2

In order to change component's state, you have to use this.setState .

constructor(props) {
    super(props);
    this.backwardWeek = this.backwardWeek.bind(this);

    this.state = {
      displayedWeek: 0,
      inputs: []

    }; 
backwardWeek() {
    this.setState({
      displayedWeek: this.state.displayedWeek - 1
    }) // notice the difference
   }

render(){

return (   
  <button onClick={this.backwardWeek}>  <span className="glyphicon glyphicon- 
   arrow-left" /></button> 
  ); // notice the difference