import React, { PureComponent } from 'react';

class LoadingBar extends PureComponent {
  render() {
    return null;
  }
}

export default LoadingBar;

import React, { PureComponent } from 'react';

class LoadingBar extends PureComponent {
  render() {
    return (
      <svg version="1.1" xmlns="http://www.w3.org/2000/svg">
        <rect />
      </svg>
    );
  }
}

export default LoadingBar;

Create SVG containing a rectangle as SVG is performance wise the best option for animation
Create SVG containing a rectangle
as SVG is performance wise the best option for animation
