block InternetExplorer <= 11 w/o Skype tel: links

block-tel-in-incapable-browser.js

(function(w) {
    w.cantel = true; // set true for all browsers
    if ("ActiveXObject" in w) { // if IE <= 11
      w.cantel = false;
      var activex;
      try { activex = !!new ActiveXObject("Skype.Detection"); } catch (e) { activex = false; }; // test for skype
      if (activex) {
        w.cantel = true;
      }
    }
    // cantel === IE+skype || MS.Edge || Other browser
    if (!w.cantel) {
      var onload = w.onload || function(){},
          links = document.getElementsByTagName("a");
      w.onload = function(){
        onload();
        var i, at;
        for(i=0; i<links.length; i++) {
          if ('tel:' == links[i].href.substr(0,4)) {
            at = links[i].getAttribute('data-alt-href') || false;
            if (at) {
              links[i].href=at;
            }
            else {
              links[i].onclick=function(){ return false; };
            }
          }
        }
      }
    }
})(window);