FCC Challenge: JS Algorithm: Telephone Number Validator

I learned a lot in this challenge. It’s important to account for the possible cases in the test phase instead of while coding. What I’m saying is that coding the solution is a different session from coming up with the test cases, this is the importance of QA Test Automation. Because, it’s easy to miss special cases when you approach the solution directly.

My approach here is to just match all the test cases instead of thinking my own test cases in my head. This is the challenge where I started to use that approach instead of making up cases while coding. I used to do the my-own-test approach just because I was thinking that the test cases might’ve missed some possible real-world scenarios (this is slightly different from security issues).

In short, I learned to trust the test cases, and focus my time on coming up with the solution instead of burning my time through imagining “troll inputs” and how to troll-proof the functions.

This is my solution developing from FCC’s test cases. Given that I’m not American to know the acceptable inputs.

function telephoneCheck(str) {
  let validCountryCode=true;
  let countryCode;

  // copy country code from original number
  countryCode = str.slice(0,2);

  // if telno. has space, compare country codes
  if(typeof str.split(" ")[1]!="undefined"){
    // if countrycode is 1 and separated by space or parentheses. its valid
    validCountryCode = countryCode=="1 "||countryCode=="1("?true:false;

  // strip away country code from original number for accurate regex
  else if(countryCode=="1 "){

  // regex for ff. special cases
  // 555-555-5555 | 5555555555 | (555)555-5555 | (555) 555-5555 | 555 555 5555
  let regex = /^\d{3}-{1}\d{3}-{1}\d{4}$|^\d{3}\d{3}\d{4}$|^[(]\d{3}[)]\s{0,1}\d{3}-\d{4}$|^\d{3}\s\d{3}\s\d{4}$/;
  if(regex.test(str)){return validCountryCode&&true;}

  return false;

Right. I mean, I think in terms of completing this specific challenge you can write to the tests and not worry about other edge cases.

In the real world, I probably would want to. If I had to write a phone number validator function, I would probably write the test cases first. This is a principle of TDD, or Test Driven Development. I don’t always do something like this, but for simple, pure functions, it makes sense to me.

Of course, you are sometimes given the boundaries of how a function should work, but with something this simple, or at least straightforward, it is not unreasonable that you would just figure it out yourself. In fact, you might even just be given a task to design a “create an account” form and just have basic user stories for that and have to figure out the validation all on your own. In this case, I’d want to come up with as many edge cases as I could because I am designing that function and it may get used in other places.

But if you’re given the test parameters like this, you could also argue that you don’t want to “gold plate” it, build in functionality that wasn’t originally requested. Sometimes it’s hard to know where the line is.

But it’s cool that you’re thinking about this stuff.

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I see that there’s a term for this: TDD. Also, I agree, it’s hard to draw the boundary. Probably the best thing to do is to grasp the concept of the required function as well as initiate in troll-proofing the code. Apply real world scenarios since what you’re generating is for the “real world”. lol.

Hey, I’ve read your story of landing your job. Thank you so much for sharing your story. It really paints a picture of what are the scenarios that one will encounter in job hunting. You’ve singlehandedly told me that landing a job is a job that you need to practice. Generally, in real life perseverance is key.

I am looking forward in landing myself a web dev job. I only have few experience in coding, 2 yrs in college plus less than a year in FCC.