How to detect a child node that contains a specific class in reactJs?

Question

I have this renderization done by reactJS

render() {

    return (
      <div>
        <Router>
          <div className="wrapper2">
            <nav id="menu-principal" className="main menu-principal">
              <ul>
                <li><NavLink className="home-link" exact to="/">início</NavLink></li>
                <li><NavLink exact to="/nota_biografica">nota biográfica</NavLink></li>

              </ul>
            </nav>
            <div className="page-content">
              <Route exact path='/nota_biografica' render={() => <NotaBiografica />} />                  
              <Route exact path='/' render={() => <Home />} />
            </div>
          </div>
        </Router>
      </div>
    )
  }

When I click on the link that contains a "home-link" class, I would like to do some action. Like an action I tried to do in the example below which didn't work. How can I solve it? Thank you.

var el = document.querySelector(".menu-principal");
      el.onclick = (event) => {                 
        for(var i = 0; i < el.childNodes.length; i++) {
          if(el.childNodes[i].className === "home-link"){
            alert('true')
          }
        }
      }

Answer 1

Because the element you targeted is <NavLink> tag which normally should navigate to another router page, I believe the event you have attached will not get running. I suggest you to not using <NavLink> just use this.props.history.push('/path/to/route') instead on the onClick handler ( after the procedures you need to run before navigating to another routing address ).

On the following example, Please pay attention about withRouter and i change <NavLink> to span then attach onHomeCLick handler to it:

import React, {Component} from 'react';
import {withRouter, Route, BrowserRouter as Router} from "react-router-dom";
class YourComponent extends Component {

  onHomeCLick = () => {
    //DO something here prior to router navigation of ".home-link" element

    this.props.history.push( '/' );
  };

  render(){
    return (
      <div>
        <Router>
          <div className="wrapper2">
            <nav id="menu-principal" className="main menu-principal">
              <ul>
                <li><span className="home-link" onClick={this.onHomeCLick}>início</span></li>
                <li><NavLink exact to="/nota_biografica">nota biográfica</NavLink></li>

              </ul>
            </nav>
            <div className="page-content">
              <Route exact path='/nota_biografica' render={() => <NotaBiografica />} />
              <Route exact path='/' render={() => <Home />} />
            </div>
          </div>
        </Router>
      </div>
    )
  }

}

export default withRouter( YourComponent );

UPDATE===========

Another trick if you like to use <NavLink> , the only solution is a "Call back" way. It will trigger once you navigated to the route ( I still can't see if there is way to do it prior to navigation ). Here we go:

import React, {Component} from 'react';
import {Route, BrowserRouter as Router} from "react-router-dom";

class YourComponent extends Component {

  isActive= (match, location) => {
    if (match) {
      console.log('Hi i am active, do something here');
    }
    return match;
  };

  render(){
    return (
      <div>
        <Router>
          <div className="wrapper2">
            <nav id="menu-principal" className="main menu-principal">
              <ul>
                <li><NavLink className="home-link" activeClassName="active" isActive={this.isActive}>início</NavLink></li>
                <li><NavLink exact to="/nota_biografica">nota biográfica</NavLink></li>

              </ul>
            </nav>
            <div className="page-content">
              <Route exact path='/nota_biografica' render={() => <NotaBiografica />} />
              <Route exact path='/' render={() => <Home />} />
            </div>
          </div>
        </Router>
      </div>
    )
  }

}

export default YourComponent;