add popper.js

public/vendor/popper.js/packages/popper/src/utils/findIndex.js

@@ -0,0 +1,21 @@
+import find from './find';
+
+/**
+ * Return the index of the matching object
+ * @method
+ * @memberof Popper.Utils
+ * @argument {Array} arr
+ * @argument prop
+ * @argument value
+ * @returns index or -1
+ */
+export default function findIndex(arr, prop, value) {
+  // use native findIndex if supported
+  if (Array.prototype.findIndex) {
+    return arr.findIndex(cur => cur[prop] === value);
+  }
+
+  // use `find` + `indexOf` if `findIndex` isn't supported
+  const match = find(arr, obj => obj[prop] === value);
+  return arr.indexOf(match);
+}