London | 26-ITP-May | Remi M. | Sprint 3 | 2-practice-tdd

Sprint-3/2-practice-tdd/count.js

@@ -1,5 +1,22 @@
+/**
+ * Counts how many times a single character appears in a string.
+ *
+ * @param {string} stringOfCharacters - The string to search through.
+ * @param {string} findCharacter - The single character to count.
+ * @returns {number} The number of times findCharacter appears in stringOfCharacters.
+ *
+ * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of
+ */
+
 function countChar(stringOfCharacters, findCharacter) {
-  return 5
+  let count = 0;
+  for (const char of stringOfCharacters) {
+    if (char === findCharacter) {
+      count++; // this means count = count + 1. This term is called 
+      // "incrementing" the count variable.
+    }
+  }
+  return count;
 }
 
 module.exports = countChar;

Sprint-3/2-practice-tdd/count.test.js

@@ -22,3 +22,20 @@ test("should count multiple occurrences of a character", () => {
 // And a character `char` that does not exist within `str`.
 // When the function is called with these inputs,
 // Then it should return 0, indicating that no occurrences of `char` were found.
+
+// test for Scenario "No Occurrences" — char isn't in the string, expect 0
+test("should return 0 when the character is not found", () => {
+  const str = "fiendish";
+  const char = "a";
+  const count = countChar(str, char);
+  expect(count).toEqual(0);
+});
+
+// extra edge case — counts 's' in "Mississippi" (should be 4)
+// Good real-world style input to make sure the loop works across a longer string.
+test("should count occurrences correctly in a mixed string", () => {
+  const str = "Apple";
+  const char = "p";
+  const count = countChar(str, char);
+  expect(count).toEqual(2);
+});

Sprint-3/2-practice-tdd/get-ordinal-number.js

@@ -1,5 +1,41 @@
+/**
+ * Converts a number into its ordinal string form (e.g. 1 → "1st", 2 → "2nd").
+ *
+ * English ordinal rules:
+ * - Numbers ending in 11, 12, or 13 always use "th" (they are exceptions).
+ * - Numbers ending in 1 (but not 11) use "st".
+ * - Numbers ending in 2 (but not 12) use "nd".
+ * - Numbers ending in 3 (but not 13) use "rd".
+ * - Everything else uses "th".
+ *
+ * @param {number} num - A positive whole number (e.g. 1, 22, 113).
+ * @returns {string} The number with its ordinal suffix appended (e.g. "1st", "22nd").
+ *
+ * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Remainder
+ * @see https://www.freecodecamp.org/news/javascript-modulo-operator/
+ */
 function getOrdinalNumber(num) {
-  return "1st";
+  // % is the "remainder" operator (also called modulo).
+  // num % 100 gives the last two digits of any number.
+  // e.g. 113 % 100 = 13, so we catch the 11/12/13 exceptions correctly.
+  const lastTwoDigits = num % 100;
+
+  // num % 10 gives the last single digit of any number.
+  // e.g. 21 % 10 = 1, so we know it ends in 1 → "st".
+  const lastDigit = num % 10;
+
+  // Check the 11/12/13 exceptions FIRST.
+  // If we checked lastDigit first, 11 would wrongly get "st" instead of "th".
+  if (lastTwoDigits === 11 || lastTwoDigits === 12 || lastTwoDigits === 13) {
+    return num + "th";
+  }
+
+  if (lastDigit === 1) return num + "st";
+  if (lastDigit === 2) return num + "nd";
+  if (lastDigit === 3) return num + "rd";
+
+  // All remaining numbers (4–9, 0, and any not caught above) use "th".
+  return num + "th";
 }
 
-module.exports = getOrdinalNumber;
+module.exports = getOrdinalNumber;

Sprint-3/2-practice-tdd/get-ordinal-number.test.js

@@ -18,3 +18,43 @@ test("should append 'st' for numbers ending with 1, except those ending with 11"
   expect(getOrdinalNumber(21)).toEqual("21st");
   expect(getOrdinalNumber(131)).toEqual("131st");
 });
+
+// Case 2: Numbers ending with 2 (but not 12)
+// When the number ends with 2, except those ending with 12,
+// Then the function should return a string by appending "nd" to the number.
+test("should append 'nd' for numbers ending with 2, except those ending with 12", () => {
+  expect(getOrdinalNumber(2)).toEqual("2nd");
+  expect(getOrdinalNumber(22)).toEqual("22nd");
+  expect(getOrdinalNumber(132)).toEqual("132nd");
+});
+
+// Case 3: Numbers ending with 3 (but not 13)
+// When the number ends with 3, except those ending with 13,
+// Then the function should return a string by appending "rd" to the number.
+test("should append 'rd' for numbers ending with 3, except those ending with 13", () => {
+  expect(getOrdinalNumber(3)).toEqual("3rd");
+  expect(getOrdinalNumber(23)).toEqual("23rd");
+  expect(getOrdinalNumber(133)).toEqual("133rd");
+});
+
+// Case 4: Numbers ending with 11, 12, or 13
+// When the number ends with 11, 12, or 13,
+// Then the function should return a string by appending "th" to the number.
+test("should append 'th' for numbers ending with 11, 12, or 13", () => {
+  expect(getOrdinalNumber(11)).toEqual("11th");
+  expect(getOrdinalNumber(12)).toEqual("12th");
+  expect(getOrdinalNumber(13)).toEqual("13th");
+});
+
+// Case 5: All other numbers
+// When the number does not end with 1, 2, or 3 (and is not an exception),
+// Then the function should return a string by appending "th" to the number.
+test("should append 'th' for all other numbers", () => {
+  expect(getOrdinalNumber(4)).toEqual("4th");
+  expect(getOrdinalNumber(10)).toEqual("10th");
+  expect(getOrdinalNumber(20)).toEqual("20th");
+  expect(getOrdinalNumber(100)).toEqual("100th");
+  expect(getOrdinalNumber(111)).toEqual("111th");
+});
+
+

Sprint-3/2-practice-tdd/repeat-str.js

@@ -1,7 +1,26 @@
-function repeatStr() {
-  // Your implementation of this function must *not* call String.prototype.repeat (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat).
-  // The goal is to re-implement that function, not to use it.
-  return "hellohellohello";
+/**
+ * Repeats a string a given number of times.
+ * This re-implements String.prototype.repeat without using it.
+ *
+ * @param {string} str - The string to repeat.
+ * @param {number} count - How many times to repeat it. Must be 0 or greater.
+ * @returns {string} The string repeated count times, or "" if count is 0.
+ * @throws {Error} If count is negative.
+ *
+ * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for
+ */
+function repeatStr(str, count) {
+  if (count < 0) {
+    throw new Error("count must be 0 or greater");
+  }
+
+  let result = "";
+
+  for (let i = 1; i < count; i++) {
+    result = result + str;
+  }
+
+  return result;
 }
 
 module.exports = repeatStr;

Sprint-3/2-practice-tdd/repeat-str.test.js

@@ -20,13 +20,28 @@ test("should repeat the string count times", () => {
 // Given a target string `str` and a `count` equal to 1,
 // When the repeatStr function is called with these inputs,
 // Then it should return the original `str` without repetition.
+test("should return the original string when count is 1", () => {
+  const str = "hello";
+  const count = 1;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("hello");
+});
 
 // Case: Handle count of 0:
 // Given a target string `str` and a `count` equal to 0,
 // When the repeatStr function is called with these inputs,
 // Then it should return an empty string.
+test("should return an empty string when count is 0", () => {
+  const str = "hello";
+  const count = 0;
+  const repeatedStr = repeatStr(str, count);
+  expect(repeatedStr).toEqual("");
+});
 
 // Case: Handle negative count:
 // Given a target string `str` and a negative integer `count`,
 // When the repeatStr function is called with these inputs,
 // Then it should throw an error, as negative counts are not valid.
+test("should throw an error when count is negative", () => {
+  expect(() => repeatStr("hello", -1)).toThrow();
+});