function updateFont (font) {
      font = font.split(' ');
      const fontSize = Number.parseInt(font.pop());
      font = font.join(' ');
      selElems.forEach((elem) => {
        if (elem && elem.getAttribute('class').includes('placemark')) {
          const elements = elem.children;
          Array.prototype.forEach.call(elements, function(i, _){
            const [ , , type ] = i.id.split('_');
            if (type === 'txt') {
              i.style.cssText = 'font-family:' + font + ';font-size:'+fontSize+';';
            }
          });
        }
      });
    }
Called when font is changed.
@param {string} font
@returns {void}