W1/3 - Time Conversion (TypeScript) (#136)

I was a in a bit of hurry last night, so I've sharpened up the first
TypeScript solution.

Correct JSDocs.
Fixed a bug in the solution where `12:00:00AM` was not returning
`00:00:00`

Author: jamiecurle

README.md

@@ -1,9 +1,9 @@
 # [Hackerrank 90 days](https://www.hackerrank.com/interview/preparation-kits/three-month-preparation-kit/three-month-week-three/challenges)
 
 
-Don't judge the layout of this repository in terms of "that's not how you lay out an Elixir project, or a Go project or a ...".  Feel free to judge me on the code in this repository. Python was my strongest language when I started this and I think that shows. I'm hoping by the time I am at the end of it all, it's harder to tell what's my strongest language.
+This repo’s layout isn’t idiomatic to any one language — Python was my strongest when I started, and it probably shows. I’m aiming to make that less obvious as I go through the challenges that by the end.
 
-If you spot anything that you think I could do better, open a pull request. That'd be lovely
+Spot something I could improve? A pull request would be lovely.
 
 
 ## 🙋 Why?

w1/tc/3_1.txt

@@ -0,0 +1,3 @@
+12:40:22AM
+
+00:40:22

w1/time_conversion.ts

@@ -1,13 +1,28 @@
+/**
+ * Time Conversion - Challenge 3 - Week 1
+ * https://www.hackerrank.com/challenges/three-month-preparation-kit-time-conversion/problem
+ * 
+ * @param s - A time string in the form 12:40:22AM
+ * @returns - A 'military' formatted time 00:40:22
+ * 
+ * @example
+ * timeConversion("12:40:22AM") // "00:40:22"
+ * timeConversion("07:05:45PM") // "19:05:45"
+ */
 export function timeConversion(s:string): string {
-    console.log(s)
     // get into parts
     const [, hourStr, minStr, secStr, period] =
     s.match(/^(\d{2}):(\d{2}):(\d{2})(AM|PM)$/)!;
 
-    // if last is PM add 12 to hour
+    // hour is the target of our meddling.
     let hour = parseInt(hourStr);
+
+    // if period is PM add 12 to hour.
     if (period === "PM" && hour !== 12) hour += 12;
 
-    // fomat and return
-    return `${hour}:${minStr}:${secStr}`
+    // if period is AM and hour is twelve, then it moves to zero.
+    if (period === "AM" && hour === 12) hour = 0;
+
+    // format and return
+    return `${hour.toString().padStart(2, "0")}:${minStr}:${secStr}`;
 }