1 files changed, 27 insertions, 0 deletions
diff --git a/src/modules/utils.js b/src/modules/utils.js
index e7f5c55..ae63b74 100644
--- a/src/modules/utils.js
+++ b/src/modules/utils.js
@@ -1,5 +1,32 @@
 const digits = /-?\d+\.?\d*/g;
 
+export function extractNum(string) {
+  return string.replace(/\D/g,'');
+}
+
+export function getTracked(trackedAndTrackerEls) {
+  const sorted = [...trackedAndTrackerEls]
+    .sort((a, b) => a.id < b.id || extractNum(a.id) <= extractNum(b.id));
+
+  const groups = [];
+  const els = sorted.slice();
+
+  while (els.length) {
+    groups.push([els.pop(), els.pop()]);
+  }
+
+  return groups;
+}
+
+export function track(targetEl, trackingEl, transformMtx) {
+  let x = targetEl.getAttributeNS(null, 'x');
+  let y = targetEl.getAttributeNS(null, 'y');
+  let ptBefore = new DOMPoint(x, y);
+  let ptAfter = ptBefore.matrixTransform(transformMtx);
+  trackingEl.setAttributeNS(null, 'x', ptAfter.x);
+  trackingEl.setAttributeNS(null, 'y', ptAfter.y);
+}
+
 export default function getComputedTransformMatrix(el) {
   const matrixSequence = getComputedStyle(el).transform.match(digits),
     identityMatrix = '';