planning

node_modules/consolidated-events/src/eventOptionsKey.js

@@ -0,0 +1,30 @@
+/* eslint-disable no-bitwise */
+
+/**
+ * Generate a unique key for any set of event options
+ */
+export default function eventOptionsKey(normalizedEventOptions) {
+  if (!normalizedEventOptions) {
+    return 0;
+  }
+
+  // If the browser does not support passive event listeners, the normalized
+  // event options will be a boolean.
+  if (normalizedEventOptions === true) {
+    return 100;
+  }
+
+  // At this point, the browser supports passive event listeners, so we expect
+  // the event options to be an object with possible properties of capture,
+  // passive, and once.
+  //
+  // We want to consistently return the same value, regardless of the order of
+  // these properties, so let's use binary maths to assign each property to a
+  // bit, and then add those together (with an offset to account for the
+  // booleans at the beginning of this function).
+  const capture = normalizedEventOptions.capture << 0;
+  const passive = normalizedEventOptions.passive << 1;
+  const once = normalizedEventOptions.once << 2;
+  return capture + passive + once;
+}
+