Merge pull request #7 from mankal111/getRandomElement

Get random element

README.md

@@ -37,6 +37,14 @@ A possible value of `randomInterval` is `[43, 75]`.
 
 The `minLength`, `maxLength` and `type` properties are optional.
 
+To get a random element from a given array:
+
+```js
+    var randomElement = JXRand.getElement([1, 2, 3]);
+```
+
+The `randomElement` should now contain one random element of the array.
+
 ## Tests
 ```
     npm test

index.js

@@ -10,6 +10,18 @@ function checkIfOptionsIsObject(options) {
   throw new TypeError(`Parameter's type is '${typeof options}' but it should be 'object'.`);
 }
 
+/**
+ * Checks if parameter is an array
+ * @param {array} array - The array parameter
+ * @returns {boolean} True if parameter is an array
+ */
+function checkIfParameterIsArray(array) {
+  if (Array.isArray(array)) {
+    return true;
+  }
+  throw new TypeError(`Parameter's type is '${typeof array}' but it should be 'array'.`);
+}
+
 /**
  * Checks if min and max have the required values
  * @param {object} options - The properties of the random number
@@ -78,9 +90,20 @@ function getInterval(options) {
   return [leftEndpoint, rightEndpoint];
 }
 
+/**
+ * Returns a random element from given array
+ * @param {array} array - The array
+ * @returns The random element
+ */
+function getRandomElement(array) {
+  checkIfParameterIsArray(array);
+  return array[getNumber({ min: 0, max: array.length - 1, type: 'integer' })];
+}
+
 const JXRand = {
   getNumber,
   getInterval,
+  getRandomElement,
 };
 
 module.exports = JXRand;

test/test.js

@@ -102,3 +102,14 @@ describe('getInterval', () => {
       .to.throw(RangeError, "'burger' is not a supported type");
   });
 });
+
+describe('getNumber', () => {
+  it('should throw an error if it is called without parameters', () => {
+    expect(() => JXRand.getRandomElement(1)).to.throw(TypeError, "Parameter's type is 'number' but it should be 'array'.");
+  });
+
+  it('should return an element of the given array', () => {
+    const givenArray = [1, 2, 3];
+    expect(givenArray.includes(JXRand.getRandomElement(givenArray))).to.equal(true);
+  });
+});