tlite.js

function tlite(getTooltipOpts) {
  document.addEventListener('mouseover', function (e) {
    var el = e.target;
    var opts = getTooltipOpts(el);

    if (!opts) {
      el = el.parentElement;
      opts = el && getTooltipOpts(el);
    }

    opts && tlite.show(el, opts, true);
  });
}

tlite.show = function (el, opts, isAuto) {
  var fallbackAttrib = 'data-tlite';
  opts = opts || {};

  (el.tooltip || Tooltip(el, opts)).show();

  function Tooltip(el, opts) {
    var tooltipEl;
    var showTimer;
    var text;

    el.addEventListener('mousedown', autoHide);
    el.addEventListener('mouseleave', autoHide);

    function show() {
      text = el.title || el.getAttribute(fallbackAttrib) || text;
      el.title = '';
      el.setAttribute(fallbackAttrib, '');
      text && !showTimer && (showTimer = setTimeout(fadeIn, isAuto ? 150 : 1))
    }

    function autoHide() {
      tlite.hide(el, true);
    }

    function hide(isAutoHiding) {
      if (isAuto === isAutoHiding) {
        showTimer = clearTimeout(showTimer);
        var parent = tooltipEl && tooltipEl.parentNode;
        parent && parent.removeChild(tooltipEl);
        tooltipEl = undefined;
      }
    }

    function fadeIn() {
      if (!tooltipEl) {
        tooltipEl = createTooltip(el, text, opts);
      }
    }

    return el.tooltip = {
      show: show,
      hide: hide
    };
  }

  function createTooltip(el, text, opts) {
    var tooltipEl = document.createElement('span');
    var grav = opts.grav || el.getAttribute('data-tlite') || 'n';

    tooltipEl.innerHTML = text;

    el.appendChild(tooltipEl);

    var vertGrav = grav[0] || '';
    var horzGrav = grav[1] || '';

    function positionTooltip() {
      tooltipEl.className = 'tlite ' + 'tlite-' + vertGrav + horzGrav;

      var arrowSize = 10;
      var top = el.offsetTop;
      var left = el.offsetLeft;

      if (tooltipEl.offsetParent === el) {
        top = left = 0;
      }

      var width = el.offsetWidth;
      var height = el.offsetHeight;
      var tooltipHeight = tooltipEl.offsetHeight;
      var tooltipWidth = tooltipEl.offsetWidth;
      var centerEl = left + (width / 2);

      tooltipEl.style.top = (
        vertGrav === 's' ? (top - tooltipHeight - arrowSize) :
        vertGrav === 'n' ? (top + height + arrowSize) :
        (top + (height / 2) - (tooltipHeight / 2))
      ) + 'px';

      tooltipEl.style.left = (
        horzGrav === 'w' ? left :
        horzGrav === 'e' ? left + width - tooltipWidth :
        vertGrav === 'w' ? (left + width + arrowSize) :
        vertGrav === 'e' ? (left - tooltipWidth - arrowSize) :
        (centerEl - tooltipWidth / 2)
      ) + 'px';
    }

    positionTooltip();

    var rect = tooltipEl.getBoundingClientRect();

    if (vertGrav === 's' && rect.top < 0) {
      vertGrav = 'n';
      positionTooltip();
    } else if (vertGrav === 'n' && rect.bottom > window.innerHeight) {
      vertGrav = 's';
      positionTooltip();
    } else if (vertGrav === 'e' && rect.left < 0) {
      vertGrav = 'w';
      positionTooltip();
    } else if (vertGrav === 'w' && rect.right > window.innerWidth) {
      vertGrav = 'e';
      positionTooltip();
    }

    tooltipEl.className += ' tlite-visible';

    return tooltipEl;
  }
};

tlite.hide = function (el, isAuto) {
  el.tooltip && el.tooltip.hide(isAuto);
};

if (typeof module !== 'undefined' && module.exports) {
  module.exports = tlite;
}