feat: add isUsername validator and fix empty string bug in isNumeric

src/index.js

@@ -1,3 +1,4 @@
+import isUsername from './lib/isUsername';
 import toDate from './lib/toDate';
 import toFloat from './lib/toFloat';
 import toInt from './lib/toInt';
@@ -246,6 +247,8 @@ const validator = {
   isLicensePlate,
   isVAT,
   ibanLocales,
+  isUsername,
+
 };
 
 export default validator;

src/lib/isNumeric.js

@@ -5,6 +5,11 @@ const numericNoSymbols = /^[0-9]+$/;
 
 export default function isNumeric(str, options) {
   assertString(str);
+
+  if (str === '' || str.length === 0) {
+    return false;
+  }
+
   if (options && options.no_symbols) {
     return numericNoSymbols.test(str);
   }

src/lib/isUsername.js

@@ -0,0 +1,15 @@
+import assertString from './util/assertString';
+
+export default function isUsername(str) {
+  assertString(str);
+  if (str.length < 3 || str.length > 15) {
+    return false;
+  }
+  for (let i = 0; i<str.length; i++) {
+    let char = str[i];
+    if (char === '@' || char === '#' || char === '$') {
+      return false;
+    }
+  }
+  return true;
+}

test/isUsername.js

@@ -0,0 +1,23 @@
+import assert from 'assert';
+import isUsername from '../src/lib/isUsername';
+
+describe('isUsername', () => {
+  it('should return true for valid usernames', () => {
+    assert.strictEqual(isUsername('roghana'), true);
+    assert.strictEqual(isUsername('user123'), true);
+  });
+
+  it('should return false if username length is less than 3', () => {
+    assert.strictEqual(isUsername('ab'), false);
+  });
+
+  it('should return false if username length is more than 15', () => {
+    assert.strictEqual(isUsername('verylongusername123'), false);
+  });
+
+  it('should return false if username contains restricted special characters', () => {
+    assert.strictEqual(isUsername('user@123'), false);
+    assert.strictEqual(isUsername('hello#'), false);
+    assert.strictEqual(isUsername('$money'), false);
+  });
+});