From c83937ed965a363ab13be1f1dbd36cd526e7f638 Mon Sep 17 00:00:00 2001
From: "M. George Hansen" <mgeorgehansen@git.theinnerlimit.ch>
Date: Tue, 26 May 2020 16:29:43 -0700
Subject: [PATCH] fix: target es2018 to support node 10+

---
 examples/personal-site/tsconfig.json |  4 ++--
 package-lock.json                    |  6 +++---
 package.json                         |  4 ++--
 src/create-element.ts                |  3 ++-
 src/utils.ts                         | 23 +++++++++++++++++++++++
 tsconfig-base.json                   |  4 ++--
 6 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/examples/personal-site/tsconfig.json b/examples/personal-site/tsconfig.json
index f155692..1cfeaeb 100644
--- a/examples/personal-site/tsconfig.json
+++ b/examples/personal-site/tsconfig.json
@@ -5,8 +5,8 @@
         "moduleResolution": "node",
         "jsx": "react",
         "jsxFactory": "createElement",
-        "target": "ES2019",
-        "lib": ["ES2019"],
+        "target": "ES2018",
+        "lib": ["ES2018"],
         "strict": true,
         "noUnusedLocals": true,
         "noUnusedParameters": true,
diff --git a/package-lock.json b/package-lock.json
index a7e8feb..cd09d0d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -62,9 +62,9 @@
             "dev": true
         },
         "@types/node": {
-            "version": "12.12.38",
-            "resolved": "https://registry.npmjs.org/@types/node/-/node-12.12.38.tgz",
-            "integrity": "sha512-75eLjX0pFuTcUXnnWmALMzzkYorjND0ezNEycaKesbUBg9eGZp4GHPuDmkRc4mQQvIpe29zrzATNRA6hkYqwmA==",
+            "version": "10.17.24",
+            "resolved": "https://registry.npmjs.org/@types/node/-/node-10.17.24.tgz",
+            "integrity": "sha512-5SCfvCxV74kzR3uWgTYiGxrd69TbT1I6+cMx1A5kEly/IVveJBimtAMlXiEyVFn5DvUFewQWxOOiJhlxeQwxgA==",
             "dev": true
         },
         "@types/ws": {
diff --git a/package.json b/package.json
index e5085f0..a37ca0d 100644
--- a/package.json
+++ b/package.json
@@ -8,7 +8,7 @@
     },
     "license": "MPL-2.0",
     "engines": {
-        "node": ">=12"
+        "node": ">=10"
     },
     "main": "dist/index.js",
     "types": "types.d.ts",
@@ -29,7 +29,7 @@
         "test": "ts-node --project=test/tsconfig.json test/run-tests.ts"
     },
     "devDependencies": {
-        "@types/node": "~12",
+        "@types/node": "~10",
         "@types/ws": "^7.2.4",
         "@typescript-eslint/eslint-plugin": "^3.0.2",
         "@typescript-eslint/parser": "^3.0.2",
diff --git a/src/create-element.ts b/src/create-element.ts
index 1163a9a..5927d75 100644
--- a/src/create-element.ts
+++ b/src/create-element.ts
@@ -5,6 +5,7 @@
 
 import { Component, Element, HTMLElement } from "./component";
 import { HTMLAttributes } from "./jsx";
+import { flatDeep } from "./utils";
 
 /**
  * Create an HTMLElement from a custom Component.
@@ -42,7 +43,7 @@ export function createElement(
     ...children: Element[]
 ): HTMLElement {
     // Flatten the children array so we can accept arrays as children.
-    const normalizedChildren = children.flat();
+    const normalizedChildren = flatDeep(children);
     if (type instanceof Function) {
         return type({ ...props, children: normalizedChildren });
     }
diff --git a/src/utils.ts b/src/utils.ts
index c8ff29b..453c2bf 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -48,3 +48,26 @@ export const purgeModuleAndDepsFromCache = (modName: string): void => {
     }
     delete require.cache[modPath];
 };
+
+export type Flattenable<T> = Array<T | Flattenable<T>>;
+
+const flatDeepRec = <T>(arr: Flattenable<T>, d: number): T[] => {
+    if (d <= 0) {
+        return arr.slice() as T[];
+    }
+
+    let acc = [] as T[];
+    for (const val of arr) {
+        acc = acc.concat(Array.isArray(val) ? flatDeepRec(arr, d - 1) : val);
+    }
+    return acc;
+};
+
+/**
+ * Flatten an arbitrarily-deeply nested array into a flat array.
+ *
+ * @param arr Array to flatten.
+ *
+ * @return Flattened array.
+ */
+export const flatDeep = <T>(arr: Flattenable<T>): T[] => flatDeepRec(arr, 1);
diff --git a/tsconfig-base.json b/tsconfig-base.json
index 84df7a5..821f547 100644
--- a/tsconfig-base.json
+++ b/tsconfig-base.json
@@ -3,8 +3,8 @@
         "esModuleInterop": true,
         "module": "CommonJS",
         "moduleResolution": "node",
-        "target": "ES2019",
-        "lib": ["ES2019"],
+        "target": "ES2018",
+        "lib": ["ES2018"],
         "strict": true,
         "noUnusedLocals": true,
         "noUnusedParameters": true,