refactor: create common validation function

utils/validate.js

@@ -0,0 +1,13 @@
+const validCharsRE = /^[a-zA-Z0-9\-_+]+$/;
+const invalidCharError = {
+  valid: false,
+  error: 'contains invalid characters'
+};
+const validationSuccess = { valid: true, error: null };
+const usernameTooShort = { valid: false, error: 'is too short' };
+
+exports.validate = str => {
+  if (str.length < 3) return usernameTooShort;
+  if (!validCharsRE.test(str)) return invalidCharError;
+  return validationSuccess;
+};

utils/validate.test.js

@@ -0,0 +1,54 @@
+/* global describe expect it */
+
+const { validate } = require('./validate');
+
+const invalidCharError = {
+  valid: false,
+  error: 'contains invalid characters'
+};
+const validationSuccess = { valid: true, error: null };
+const usernameTooShort = { valid: false, error: 'is too short' };
+
+function inRange(num, range) {
+  return num >= range[0] && num <= range[1];
+}
+
+describe('validate', () => {
+  it('rejects strings with less than 3 characters', () => {
+    expect(validate('')).toStrictEqual(usernameTooShort);
+    expect(validate('12')).toStrictEqual(usernameTooShort);
+    expect(validate('a')).toStrictEqual(usernameTooShort);
+    expect(validate('123')).toStrictEqual(validationSuccess);
+  });
+  it('rejects non-ASCII characters', () => {
+    expect(validate('👀👂👄')).toStrictEqual(invalidCharError);
+  });
+  it('accepts alphanumeric characters', () => {
+    expect(validate('abcdefghijklmnopqrstuvwxyz0123456789')).toStrictEqual(
+      validationSuccess
+    );
+  });
+  it('accepts hyphens and underscores', () => {
+    expect(validate('a-b')).toStrictEqual(validationSuccess);
+    expect(validate('a_b')).toStrictEqual(validationSuccess);
+  });
+
+  it('rejects all other ASCII characters', () => {
+    const whiteList = ['-', '_', '+'];
+    const numbers = [48, 57];
+    const upperCase = [65, 90];
+    const lowerCase = [97, 122];
+    const base = 'user';
+    const finalCode = 127;
+
+    for (let code = 0; code <= finalCode; code++) {
+      let char = String.fromCharCode(code);
+      let expected = invalidCharError;
+      if (whiteList.includes(char)) expected = validationSuccess;
+      if (inRange(code, numbers)) expected = validationSuccess;
+      if (inRange(code, upperCase)) expected = validationSuccess;
+      if (inRange(code, lowerCase)) expected = validationSuccess;
+      expect(validate(base + char)).toStrictEqual(expected);
+    }
+  });
+});