How to prevent React from posting back when submit button is pressed

<a id="mySubmit" href="#">
<img border="0" alt="Submit Request" src="submit_btn.gif">
</a>

$("#mySubmit").click(function(event) {
    $(this).hide();
    // do other stuff here
    return(false);
});

<img id="mySubmit" border="0" alt="Submit Request" src="submit_btn.gif">

$("#mySubmit").click(function(event) {
    $(this).hide();
    // do other stuff here
    return(false);
});

class MyComponent extends Component {
    state = {};
    componentDidMount(){
         BackHandler.addEventListener('hardwareBackPress', this.backHandler);
    }
    componentWillUnmount(){
         BackHandler.removeEventListener('hardwareBackPress', this.backHandler);
    }
    backHandler = () => {
        if(this.state.backButtonEnabled) {
            this.refs[WEBVIEW_REF].goBack();
            return true;
        }
    }
}

validateForm = e => {
    e.preventDefault(); 
    // your code here
}

validateForm = function(e) {
    console.log('Hello world');
    console.log(e);
}

    this.platform.backButton.subscribe(()=> {
         const alert = await this.alertController.create({
         header: 'Confirm!',
         message: 'Do you want to go back!!!',
         buttons: [
         {
            text: 'Yes',
            handler: () => {
            // Previous page loaded
         }
         }, {
            text: 'No',
            handler: () => {
            reject()
              }
            }
         ]
      });
    })

<Scene 
         key="latest"
         title="LATEST"
         titleStyle={{flex:0}}
         component={Latest}
         onRight={()=>{}} 
         rightButtonImage={NOTIFICATION_ICON}
         onLeft={()=>{}}
         leftButtonImage={NAV_SEARCH_ICON}
/>

componentDidMount() {
          this.props.navigation.setParams({
               'onRight': this.showNotifications,
               'onLeft': this.showSearch,
         })
  }