Create maximum function and maximum spec file

index.js

@@ -15,6 +15,7 @@ module.exports = Object.assign(
   require('./lib/isAscending.js'),
   require('./lib/isDescending.js'),
   require('./lib/isPrime.js'),
+  require('./lib/maximum.js'),
   require('./lib/median.js'),
   require('./lib/mode.js'),
   require('./lib/populationStandardDeviation.js'),

lib/maximum.js

@@ -0,0 +1,21 @@
+const { floatPrecise } = require('./floatPrecise');
+
+const handleErrors = (params) => {
+  if (params.length === 0) throw new Error('Must provide one or more paramters');
+  if (params.some(param => typeof param !== 'number')) {
+    throw new Error('One of your parameters does not evaluate to a number');
+  }
+  // JS can only safely represent and compare integers
+  // between Number.MAX_SAFE_INTEGER and Number.MAX_SAFE_INTEGER
+  if (params.some(param => param > Number.MAX_SAFE_INTEGER || param < Number.MIN_SAFE_INTEGER)) {
+    throw new Error('Cannot reliably test primality of numbers larger than 9,007,199,254,740,991 or smaller than -9,007,199,254,740,991');
+  }
+};
+
+exports.maximum = (...params) => {
+  handleErrors(params);
+
+  const result = params.reduce((prev, cur) => (cur > prev ? cur : prev));
+
+  return floatPrecise(result);
+};

spec/maximumSpec.js

@@ -0,0 +1,24 @@
+const { maximum } = require('../lib/maximum');
+
+describe('maximum', () => {
+  it('should return the maximum of all parameters, given that all parameters evaluate to numbers', () => {
+    const result = maximum(1, 5, -7, 15, 10);
+    expect(result).toBe(15);
+  });
+
+  it('should throw an error when no parameters are provided', () => {
+    expect(maximum).toThrow();
+  });
+
+  it('should throw an error when at least one parameter does not evaluate to a number', () => {
+    expect(() => maximum('yo')).toThrow();
+  });
+
+  it('should throw an error when at least one parameter evaluates to a number larger than Number.MAX_SAFE_INTEGER', () => {
+    expect(() => maximum(Number.MAX_SAFE_INTEGER + 1)).toThrow();
+  });
+
+  it('should throw an error when at least one parameter evaluates to a number smaller than Number.MIN_SAFE_INTEGER', () => {
+    expect(() => maximum(Number.MIN_SAFE_INTEGER - 1)).toThrow();
+  });
+});