grafana/public/app/core/utils/outline.ts

// based on http://www.paciellogroup.com/blog/2012/04/how-to-remove-css-outlines-in-an-accessible-manner/
function outlineFixer() {
  const d: any = document;

  const styleElement = d.createElement('STYLE');
  const domEvents = 'addEventListener' in d;

  const addEventListener = (type: string, callback: { (): void; (): void }) => {
    // Basic cross-browser event handling
    if (domEvents) {
      d.addEventListener(type, callback);
    } else {
      d.attachEvent('on' + type, callback);
    }
  };

  const setCss = (cssText: string) => {
    // Handle setting of <style> element contents in IE8
    !!styleElement.styleSheet ? (styleElement.styleSheet.cssText = cssText) : (styleElement.innerHTML = cssText);
  };

  d.getElementsByTagName('HEAD')[0].appendChild(styleElement);

  // Using mousedown instead of mouseover, so that previously focused elements don't lose focus ring on mouse move
  addEventListener('mousedown', () => {
    setCss(':focus{outline:0 !important}::-moz-focus-inner{border:0;}');
  });

  addEventListener('keydown', () => {
    setCss('');
  });
}

outlineFixer();