refactor code to be simpler and remove dependency

package.json

@@ -24,9 +24,7 @@
   "bugs": {
     "url": "https://github.com/malcolm-kee/join-string/issues"
   },
-  "dependencies": {
-    "typesafe-is": "^1.0.1"
-  },
+  "dependencies": {},
   "devDependencies": {
     "@types/jest": "^23.3.9",
     "coveralls": "^3.0.2",

src/index.ts

@@ -1,20 +1,26 @@
-import { isFilledString, isArray, isNumber } from 'typesafe-is';
+type JoinFunction = (...items: any[]) => string;
 
-export const joinString = (delimiter: string) =>
-  function joinFn(...items: Array<any>): string {
+export const joinString = (delimiter: string): JoinFunction =>
+  function joinFn(): string {
     const results: Array<string | number> = [];
 
-    for (let index = 0; index < items.length; index++) {
-      const item = items[index];
+    for (let index = 0; index < arguments.length; index++) {
+      const item = arguments[index];
 
-      if (isNumber(item) || isFilledString(item)) {
+      if (!item && item !== 0) continue;
+
+      const itemType = typeof item;
+
+      if (itemType == 'string' || itemType == 'number') {
         results.push(item);
         continue;
       }
 
-      if (isArray(item)) {
-        results.push(joinFn(...item));
-        continue;
+      if (Array.isArray(item) && item.length > 0) {
+        const innerResult = joinFn.apply(null, item);
+        if (innerResult) {
+          results.push(innerResult);
+        }
       }
     }
 

test/index.spec.ts

@@ -18,7 +18,9 @@ describe('joinString', () => {
 
   test('array will be flatten', () => {
     const joinFn = joinString(', ');
-    expect(joinFn('x', false, undefined, 'y', [false, null, 'z', ''])).toBe('x, y, z');
+    expect(joinFn('x', false, undefined, [false], 'y', [false, null, 'z', ''])).toBe(
+      'x, y, z'
+    );
   });
 });
 

yarn.lock

@@ -3450,11 +3450,6 @@ type-check@~0.3.2:
   dependencies:
     prelude-ls "~1.1.2"
 
-typesafe-is@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/typesafe-is/-/typesafe-is-1.0.1.tgz#eb86c4276eb27d0e9a99f4c7efd509175a3c2ef0"
-  integrity sha512-nDxlJeNidbMHAtZg5iWsEJzvLPfiljWxgoRwb0M6uE7FMHD8/blNLclILO3/n7rF8refTSeZ2Pm1e9edf4Detg==
-
 typescript@^3.1.6:
   version "3.1.6"
   resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.1.6.tgz#b6543a83cfc8c2befb3f4c8fba6896f5b0c9be68"