function convert() {
  // source content  
  var source = document.getElementById("source").value;
  // all gradients expression
  var gradientExp = /(<[a-zA-Z]+Gradient[\S\s]+?<\/[a-zA-Z]+Gradient>)/g;
  // finding all gradients  
  var gradientMatches = source.match(gradientExp);
  // gradients array to hold gradient objects for comparison
  var gradients = [];
  // if any gradients exist  
  if(gradientMatches) {
    // for each match
    for (var m = 0; m < gradientMatches.length;) {
      
      var gradient = gradientMatches[m++],
          tag = gradient.match(/<[a-zA-Z]+Gradient[\S\s]+?>/)[0],
          type = tag.match(/[a-z]+Gradient/)[0],
          id = tag.match(/id=".*?"/)[0].replace(/id="(.*)?"/, "$1"),
          attrs = tag.match(/[a-zA-Z0-9-_]+=".+?"/g),
          stops = "  " + gradient.match(/<stop.*(\/>|<\/stop>)/g).join("\n  "); 
    
      // if we're past the first match
      if (m > 1) {
        // checking flag
        var checking = true;
        // see if stops match a previous stops
        for (var s = m - 1; s > 0; s--) {
          // if stops match previous stops
          if (stops == gradients[s - 1].stops && checking) {
            checking = false;
            // remove stops value
            stops = "";// "#" + gradients[s - 1].id;
            // add xlink attribute
            attrs.splice(1, 0, "xlink:href=\"#" + gradients[s - 1].id + "\"");
          };
        }
      }
      
      // add gradient to gradients
      gradients.push({
        type: type,
        id: id,
        attrs: attrs,
        stops: stops
      });
      
      // remove all gradients
      source = source.replace(gradient, "");
    }

    console.log(gradients);
    
    // defs
    var defs = "";
    // for each gradient
    for(var g = 0; g < gradients.length; g++) {
      var gradient = gradients[g];      
      defs += "\n<" + gradient.type + " " + gradient.attrs.join(" ");
      if (gradient.stops) {
        defs += ">\n" + gradient.stops + "\n</" + gradient.type + ">";
      } else {
        defs += " />";
      }
      defs += "\n";
    }
    
    if(source.indexOf("<defs>") > -1) {
      source = source.replace("<defs>", "<defs>\n"+defs);
    } else {
      source = source.replace(/(<svg.*?>)/g, "$1\n<defs>\n"+defs+"</defs>\n");
    }
    
  }
  document.getElementById("output").value = source;
}