Add weightedSample snippet

test/weightedSample.test.js

@@ -0,0 +1,16 @@
+const {weightedSample} = require('./_30s.js');
+
+test('sample is a Function', () => {
+  expect(weightedSample).toBeInstanceOf(Function);
+});
+const arr = [3, 7, 9, 11];
+const weights = [0.1, 0.2, 0.6, 0.1];
+test('Returns a random element from the array', () => {
+  expect(arr.includes(weightedSample(arr, weights))).toBeTruthy();
+});
+test('Works for single-element arrays', () => {
+  expect(weightedSample([1], [1])).toBe(1);
+});
+test('Returns undefined for empty array', () => {
+  expect(weightedSample([], [])).toBe(undefined);
+});