feat: add primes in range algorithm

Maths/PrimesInRange.js

@@ -0,0 +1,38 @@
+/**
+ * @function primesInRange
+ * @description Returns all prime numbers in a given range [start, end]
+ *   using the Sieve of Eratosthenes algorithm.
+ * @param {number} start - The start of the range (inclusive)
+ * @param {number} end - The end of the range (inclusive)
+ * @returns {number[]} - Array of all prime numbers in the range
+ * @see https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
+ * @example primesInRange(1, 10) => [2, 3, 5, 7]
+ * @example primesInRange(10, 20) => [11, 13, 17, 19]
+ */
+const primesInRange = (start, end) => {
+  if (!Number.isInteger(start) || !Number.isInteger(end)) {
+    throw new TypeError('Both inputs must be integers')
+  }
+  if (start < 1 || end < 1) {
+    throw new TypeError('Both inputs must be positive integers')
+  }
+  if (start > end) {
+    throw new RangeError('Start must be less than or equal to end')
+  }
+  const sieve = new Array(end + 1).fill(true)
+  sieve[0] = false
+  sieve[1] = false
+  for (let i = 2; i <= Math.sqrt(end); i++) {
+    if (sieve[i]) {
+      for (let j = i * i; j <= end; j += i) {
+        sieve[j] = false
+      }
+    }
+  }
+  return sieve
+    .slice(start)
+    .map((isPrime, i) => (isPrime ? start + i : null))
+    .filter((n) => n !== null)
+}
+
+export { primesInRange }

Maths/test/PrimesInRange.test.js

@@ -0,0 +1,43 @@
+import { primesInRange } from '../PrimesInRange.js'
+
+describe('primesInRange', () => {
+  test('primesInRange(1, 10) returns [2,3,5,7]', () => {
+    expect(primesInRange(1, 10)).toEqual([2, 3, 5, 7])
+  })
+
+  test('primesInRange(10, 20) returns [11,13,17,19]', () => {
+    expect(primesInRange(10, 20)).toEqual([11, 13, 17, 19])
+  })
+
+  test('primesInRange(1, 2) returns [2]', () => {
+    expect(primesInRange(1, 2)).toEqual([2])
+  })
+
+  test('primesInRange(1, 1) returns []', () => {
+    expect(primesInRange(1, 1)).toEqual([])
+  })
+
+  test('primesInRange(14, 16) returns []', () => {
+    expect(primesInRange(14, 16)).toEqual([])
+  })
+
+  test('primesInRange(1, 50) has correct count', () => {
+    expect(primesInRange(1, 50)).toHaveLength(15)
+  })
+
+  test('primesInRange with same start and end that is prime', () => {
+    expect(primesInRange(7, 7)).toEqual([7])
+  })
+
+  test('throws TypeError for float input', () => {
+    expect(() => primesInRange(1.5, 10)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for negative input', () => {
+    expect(() => primesInRange(-1, 10)).toThrow(TypeError)
+  })
+
+  test('throws RangeError when start > end', () => {
+    expect(() => primesInRange(10, 5)).toThrow(RangeError)
+  })
+})