Add combineURLs helper

lib/helpers/combineURLs.js

+'use strict';
+
+/**
+ * Creates a new URL by combining the specified URLs
+ *
+ * @param {string} baseURL The base URL
+ * @param {string} relativeURL The relative URL
+ * @returns {string} The combined URL
+ */
+module.exports = function combineURLs(baseURL, relativeURL) {
+  return baseURL.replace(/\/+$/, '') + '/' + relativeURL.replace(/^\/+/, '');
+};

test/specs/helpers/combineURLs.spec.js

+var combineURLs = require('../../../lib/helpers/combineURLs');
+
+describe('helpers::combineURLs', function () {
+  it('should combine URLs', function () {
+    expect(combineURLs('https://api.github.com', '/users')).toBe('https://api.github.com/users');
+  });
+
+  it('should remove duplicate slashes', function () {
+    expect(combineURLs('https://api.github.com/', '/users')).toBe('https://api.github.com/users');
+  });
+
+  it('should insert missing slash', function () {
+    expect(combineURLs('https://api.github.com', 'users')).toBe('https://api.github.com/users');
+  });
+});