Complete telephone number algorithm

Author: ahcode0919

src/fcc-course-projects/fcc_course_projects.md

@@ -7,6 +7,7 @@ From the Freecodecamp Javascript Certification Algorithms Projects module
 - [Palindrome Checker](#palindrome-checker)
 - [Roman Numeral Converter](#roman-numeral-converter)
 - [Caesars Cipher](#caesars-cipher)
+- [Telephone Number Validator](#telephone-number-validator)
 
 #### Palindrome Checker
 
@@ -79,3 +80,26 @@ export function rot13(str) {
   return decoded.join('');
 }
 ```
+
+#### Telephone Number Validator
+
+Return `true` if the passed string looks like a valid US phone number.
+
+The user may fill out the form field any way they choose as long as it has the format of a valid US number. The following are examples of valid formats for US numbers (refer to the tests below for other variants):
+
+```text
+555-555-5555
+(555)555-5555
+(555) 555-5555
+555 555 5555
+5555555555
+1 555 555 5555
+```
+
+For this challenge you will be presented with a string such as `800-692-7753` or `8oo-six427676;laskdjf`. Your job is to validate or reject the US phone number based on any combination of the formats provided above. The area code is required. If the country code is provided, you must confirm that the country code is 1. Return true if the string is a valid US phone number; otherwise return false.
+
+```javascript
+export function telephoneCheck(str) {
+  return /^(1 ?)?(\([0-9]{3}\)|[0-9]{3})[ \-]?[0-9]{3}[ \-]?[0-9]{4}$$/.test(str);
+}
+```

src/fcc-course-projects/telephone_number.js

@@ -0,0 +1,3 @@
+export function telephoneCheck(str) {
+  return /^(1 ?)?(\([0-9]{3}\)|[0-9]{3})[ \-]?[0-9]{3}[ \-]?[0-9]{4}$/.test(str);
+}

tests/fcc-course-projects/telephone_number.test.js

@@ -0,0 +1,10 @@
+import { telephoneCheck } from "../../src/fcc-course-projects/telephone_number";
+
+test('should check telephone numbers', () => {
+  expect(telephoneCheck("2323dfsf")).toBe(false);
+  expect(telephoneCheck("5555555555")).toBe(true);
+  expect(telephoneCheck("1 555-555-5555")).toBe(true);
+  expect(telephoneCheck("555-555-5555")).toBe(true);
+  expect(telephoneCheck("1 555)555-5555")).toBe(false);
+  expect(telephoneCheck("(6054756961)")).toBe(false);
+});