added object/array compare utils.

Author: varun93

compare.js

@@ -0,0 +1,64 @@
+const compareArrays = (arrayA, arrayB) => {
+  let isEqual = true;
+
+  if (arrayA == null && arrayB === null) {
+    return true;
+  }
+
+  if (arrayA.length !== arrayB.length) {
+    return false;
+  }
+
+  for (var index = 0; index < arrayA.length; index++) {
+    const elementA = arrayA[index];
+    const elementB = arrayB[index];
+
+    if (typeof elementA !== typeof elementB) {
+      isEqual = false;
+      break;
+    }
+
+    if (Array.isArray(elementA)) {
+      isEqual &= compareArrays(elementA, elementB);
+    } else if (typeof elementA === "object") {
+      isEqual &= compareObjects(elementA, elementB);
+    } else {
+      isEqual &= elementA === elementB;
+    }
+
+    if (!isEqual) {
+      break;
+    }
+  }
+
+  return isEqual;
+};
+
+// yes JSON.stringify(objA) === JSON.stringify(objB) works for shallow comapare, but doesn't work for deep compare!
+const compareObjects = (objA, objB) => {
+  if (objA === null && objB === null) {
+    return true;
+  }
+  const objAKeys = Object.keys(objA);
+  const objBKeys = Object.keys(objB);
+
+  if (objAKeys.length !== objBKeys.length) {
+    return false;
+  }
+
+  return objAKeys.reduce((isEqual, keyA) => {
+    const elemA = objA[keyA];
+    const elemB = objB[keyA];
+    isEqual &= typeof elemA === typeof elemA;
+
+    if (Array.isArray(elemA)) {
+      isEqual &= compareArrays(elemA, elemB);
+    } else if (typeof elemA === "object") {
+      isEqual &= compareObjects(elemA, elemB);
+    } else {
+      isEqual &= elemA === elemB;
+    }
+
+    return isEqual;
+  }, true);
+};