Add an algorithm to find Taylor series approximation of exponential f… (TheAlgorithms#1160)

Author: prashalruchiranga

Maths/ExponentialFunction.js

@@ -0,0 +1,25 @@
+/**
+ * @function exponentialFunction
+ * @description Calculates the n+1 th order Taylor series approximation of exponential function e^x given n
+ * @param {Integer} power
+ * @param {Integer} order - 1
+ * @returns exponentialFunction(2,20) = 7.3890560989301735
+ * @url https://en.wikipedia.org/wiki/Exponential_function
+ */
+function exponentialFunction (power, n) {
+  let output = 0
+  let fac = 1
+  if (isNaN(power) || isNaN(n) || n < 0) {
+    throw new TypeError('Invalid Input')
+  }
+  if (n === 0) { return 1 }
+  for (let i = 0; i < n; i++) {
+    output += (power ** i) / fac
+    fac *= (i + 1)
+  }
+  return output
+}
+
+export {
+  exponentialFunction
+}

Maths/test/ExponentialFunction.test.js

@@ -0,0 +1,16 @@
+import { exponentialFunction } from '../ExponentialFunction'
+
+describe('Tests for exponential function', () => {
+  it('should be a function', () => {
+    expect(typeof exponentialFunction).toEqual('function')
+  })
+
+  it('should throw error for invalid input', () => {
+    expect(() => exponentialFunction(2, -34)).toThrow()
+  })
+
+  it('should return the exponential function of power of 5 and order of 21', () => {
+    const ex = exponentialFunction(5, 20)
+    expect(ex).toBe(148.4131078683383)
+  })
+})