diff --git a/packages/babel-parser/src/parser/lval.js b/packages/babel-parser/src/parser/lval.js
index 1a9a690388..2d1f13ad2e 100644
--- a/packages/babel-parser/src/parser/lval.js
+++ b/packages/babel-parser/src/parser/lval.js
@@ -149,12 +149,10 @@ export default class LValParser extends NodeUtils {
         const arg = last.argument;
         this.toAssignable(arg, isBinding, contextDescription);
         if (
-          [
-            "Identifier",
-            "MemberExpression",
-            "ArrayPattern",
-            "ObjectPattern",
-          ].indexOf(arg.type) === -1
+          arg.type !== "Identifier" &&
+          arg.type !== "MemberExpression" &&
+          arg.type !== "ArrayPattern" &&
+          arg.type !== "ObjectPattern"
         ) {
           this.unexpected(arg.start);
         }
@@ -430,13 +428,12 @@ export default class LValParser extends NodeUtils {
   }
 
   checkToRestConversion(node: SpreadElement): void {
-    const validArgumentTypes = ["Identifier", "MemberExpression"];
-
-    if (validArgumentTypes.indexOf(node.argument.type) !== -1) {
-      return;
+    if (
+      node.argument.type !== "Identifier" &&
+      node.argument.type !== "MemberExpression"
+    ) {
+      this.raise(node.argument.start, "Invalid rest operator's argument");
     }
-
-    this.raise(node.argument.start, "Invalid rest operator's argument");
   }
 
   checkCommaAfterRest(close: TokenType, kind: string): void {
diff --git a/packages/babel-parser/src/parser/node.js b/packages/babel-parser/src/parser/node.js
index 73223eea85..5ed447018d 100644
--- a/packages/babel-parser/src/parser/node.js
+++ b/packages/babel-parser/src/parser/node.js
@@ -7,8 +7,6 @@ import type { Comment, Node as NodeType, NodeBase } from "../types";
 
 // Start an AST node, attaching a start offset.
 
-const commentKeys = ["leadingComments", "trailingComments", "innerComments"];
-
 class Node implements NodeBase {
   constructor(parser: Parser, pos: number, loc: Position) {
     this.type = "";
@@ -34,7 +32,11 @@ class Node implements NodeBase {
     const node2: any = new Node();
     Object.keys(this).forEach(key => {
       // Do not clone comments that are already attached to the node
-      if (commentKeys.indexOf(key) < 0) {
+      if (
+        key !== "leadingComments" &&
+        key !== "trailingComments" &&
+        key !== "innerComments"
+      ) {
         // $FlowIgnore
         node2[key] = this[key];
       }