feat: add geometry triangle

Author: saahil-mahato

Geometry/Test/Triangle.test.js

@@ -0,0 +1,43 @@
+import Triangle from '../Triangle'
+
+describe('Triangle', () => {
+  describe('Triangle created with sides', () => {
+    const triangle = new Triangle(3, 4, 5)
+
+    test('The area of a triangle with sides 3, 4, 5', () => {
+      expect(parseFloat(triangle.area().toFixed(2))).toEqual(6.0)
+    })
+
+    test('The perimeter of a triangle with sides 3, 4, 5', () => {
+      expect(parseFloat(triangle.perimeter().toFixed(2))).toEqual(12.0)
+    })
+  })
+
+  describe('Triangle created with base and height', () => {
+    const triangle = new Triangle(6, 4)
+
+    test('The area of a triangle with base 6 and height 4', () => {
+      expect(parseFloat(triangle.area().toFixed(2))).toEqual(12.0)
+    })
+
+    test('The perimeter calculation throws an error for base-height triangle', () => {
+      expect(() => triangle.perimeter()).toThrow(
+        'Cannot calculate perimeter: not all sides are known.'
+      )
+    })
+  })
+
+  describe('Invalid triangle creation', () => {
+    test('Creating a triangle with invalid sides throws an error', () => {
+      expect(() => new Triangle(1, 1, 10)).toThrow(
+        'Invalid triangle: The sum of any two sides must be greater than the third side.'
+      )
+    })
+
+    test('Creating a triangle with invalid number of arguments throws an error', () => {
+      expect(() => new Triangle(1)).toThrow(
+        'Invalid number of arguments. Use either (base, height) or (sideA, sideB, sideC).'
+      )
+    })
+  })
+})

Geometry/Triangle.js

@@ -0,0 +1,95 @@
+/**
+ * This class represents a Triangle and can calculate its area and perimeter with either all three sides or the base and height.
+ * https://en.wikipedia.org/wiki/Triangle
+ * @class
+ */
+export default class Triangle {
+  /**
+   * Create a triangle.
+   * @constructor
+   * @param {...number} args - The triangle dimensions.
+   * @throws {Error} Will throw an error if the number of arguments is invalid or if the triangle is invalid.
+   */
+  constructor(...args) {
+    if (args.length === 2) {
+      this.initializeFromBaseAndHeight(...args)
+    } else if (args.length === 3) {
+      this.initializeFromSides(...args)
+    } else {
+      throw new Error(
+        'Invalid number of arguments. Use either (base, height) or (sideA, sideB, sideC).'
+      )
+    }
+  }
+
+  /**
+   * Initialize the triangle from base and height.
+   * @param {number} base - The base of the triangle.
+   * @param {number} height - The height of the triangle.
+   * @private
+   */
+  initializeFromBaseAndHeight = (base, height) => {
+    this.base = base
+    this.height = height
+    this.sides = [base, null, null]
+  }
+
+  /**
+   * Initialize the triangle from three sides.
+   * @param {number} sideA - The length of side A.
+   * @param {number} sideB - The length of side B.
+   * @param {number} sideC - The length of side C.
+   * @throws {Error} Will throw an error if the triangle is invalid.
+   * @private
+   */
+  initializeFromSides = (sideA, sideB, sideC) => {
+    if (!this.isValidTriangle(sideA, sideB, sideC)) {
+      throw new Error(
+        'Invalid triangle: The sum of any two sides must be greater than the third side.'
+      )
+    }
+    this.sides = [sideA, sideB, sideC]
+    this.base = sideA
+    this.height = null
+  }
+
+  /**
+   * Check if three sides can form a valid triangle.
+   * @param {number} a - The length of side A.
+   * @param {number} b - The length of side B.
+   * @param {number} c - The length of side C.
+   * @returns {boolean} True if the triangle is valid, false otherwise.
+   * @private
+   */
+  isValidTriangle = (a, b, c) => {
+    return a + b > c && b + c > a && c + a > b
+  }
+
+  /**
+   * Calculate the area of the triangle.
+   * @returns {number} The area of the triangle.
+   * @public
+   */
+  area = () => {
+    if (this.height !== null) {
+      return 0.5 * this.base * this.height
+    }
+    // Using Heron's formula
+    const [a, b, c] = this.sides
+    const s = (a + b + c) / 2
+    return Math.sqrt(s * (s - a) * (s - b) * (s - c))
+  }
+
+  /**
+   * Calculate the perimeter of the triangle.
+   * @returns {number} The perimeter of the triangle.
+   * @throws {Error} Will throw an error if not all sides are known.
+   * @public
+   */
+  perimeter = () => {
+    if (this.sides.some((side) => side === null)) {
+      throw new Error('Cannot calculate perimeter: not all sides are known.')
+    }
+    return this.sides.reduce((sum, side) => sum + side, 0)
+  }
+}