Iterate through 2D array in React

gistfile1.txt

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';

class App extends Component {
  constructor(props) {
    super(props);

    this.state = {
      data: [[1,1,0,1,1,1],[1,1,1]]
    };
  }


  componentDidMount = () => {
    const data = this.state.data;
    var counter = 0;
    for(var i = 0; i < data.length; i++) {
      for(var j = 0; j < data[i].length; j++) {
        counter += data[i][j];
      }
    }
    console.log(counter);
  }

  render() {
    return (
      <div className="App">
        <header className="App-header">
          <img src={logo} className="App-logo" alt="logo" />
          <h1 className="App-title">Welcome to React</h1>
        </header>
        <p className="App-intro">
          To get started, edit <code>src/App.js</code> and save to reload.
        </p>
      </div>
    );
  }
}

export default App;