developher-net
diff --git a/‎2023/day-01/checksum.js
Lines changed: 8 additions & 3 deletions b/‎2023/day-01/checksum.js
Lines changed: 8 additions & 3 deletions
diff --git a/‎2023/day-01/checksum.test.js
Lines changed: 4 additions & 1 deletion b/‎2023/day-01/checksum.test.js
Lines changed: 4 additions & 1 deletion
@@ -4,9 +4,14 @@
  * @param string containing a single line of data
  */
 const checksumLine = (data) => {
-  data.replace(/([^0-9])+/g, '') // trim non-numeric characters
-  const checksumString = `${data[0]}${data[-1]}`
-  return parseInt(checksumString)
+  const parsed = data.replace(/([^0-9])/g, '') // trim non-numeric characters
+  let result = ''
+  if (parsed.length === 1) { // some strings only have a single digit
+    result = `${parsed}${parsed}`
+  } else {
+    result = `${parsed[0]}${parsed[parsed.length - 1]}`
+  }
+  return parseInt(result)
 }
 
 /**
 
@@ -8,8 +8,11 @@ describe('--- Day 1: Trebuchet?! ---', () => {
       it('calculates the checksum for a string by concatentating the first and last number', () => {
         // provided
         expect(checksumLine('1abc2')).to.equal(12)
-        expect(checksumLine('pqr3stu8vwx')).to.equal(18)
+        expect(checksumLine('pqr3stu8vwx')).to.equal(38)
         expect(checksumLine('a1b2c3d4e5f')).to.equal(15)
+      })
+      it('handles the edge case of a line with only a single digit', () => {
+        // provided
         expect(checksumLine('treb7uchet')).to.equal(77)
       })
     })