From 16efb013eb62bb3630b0375ad7a054820aa2382c Mon Sep 17 00:00:00 2001
From: Jason Johnston <jason.johnston@protectwise.com>
Date: Wed, 19 Feb 2020 21:04:30 -0700
Subject: [PATCH] feat: Add memoize function in utils

---
 packages/troika-core/src/utils.js | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/packages/troika-core/src/utils.js b/packages/troika-core/src/utils.js
index 20e4822e..4bbaf71b 100644
--- a/packages/troika-core/src/utils.js
+++ b/packages/troika-core/src/utils.js
@@ -105,6 +105,34 @@ export const getIdForObject = (() => {
 })()
 
 
+/**
+ * Create a function that memoizes the result of another function based on the most
+ * recent call's arguments and `this`. The arguments are compared using strict shallow equality.
+ * @param {function} fn
+ * @return {function}
+ */
+export function memoize(fn) {
+  let prevArgs, prevThis, prevResult
+  return function() {
+    let changed = !prevArgs || this !== prevThis || arguments.length !== prevArgs.length
+    if (!changed) {
+      for (let i = 0, len = arguments.length; i < len; i++) {
+        if (arguments[i] !== prevArgs[i]) {
+          changed = true
+          break
+        }
+      }
+    }
+    if (changed) {
+      prevArgs = Array.prototype.slice.call(arguments)
+      prevThis = this
+      prevResult = fn.apply(this, arguments)
+    }
+    return prevResult
+  }
+}
+
+
 /**
  * Utility for the "extend-as" pattern used in several places to decorate facade
  * classes with extra capabilities.