4 done

tests/problem1.test.js

@@ -9,6 +9,22 @@
 
 */
 
+function groupBy(numbersTable, groupFunction) {
+    return numbersTable.reduce((groupedNumbers, number) => {
+        const groupName = groupFunction(number) + '';
+
+    console.log(groupedNumbers)
+
+    if (!groupedNumbers[groupName]) {
+        groupedNumbers[groupName] = [];
+    }
+
+    groupedNumbers[groupName].push(number);
+
+    return groupedNumbers;
+}, {});
+}
+
 describe('problem1 - groupBy', () => {
     it('returns an object', () => {
         expect(groupBy([1, 2, 3], v => v)).toBeInstanceOf(Object);

tests/problem2.test.js

@@ -16,6 +16,14 @@
     greetButVeryLoud('John') // HELLO JOHN!!!!!!!!1111one
 */
 
+function compose(...functions) {
+    return function(something) {
+        return functions.reduce((changedSomething, currentFunction) => {
+            return currentFunction(changedSomething);
+        }, something);
+    }
+}
+
 describe('problem2 - compose', () => {
     function stringToNumber(s) {
         return parseInt(s);

tests/problem3.test.js

@@ -28,6 +28,20 @@
 
 */
 
+function curry(func) {
+    const argumentsLength = func.length;
+
+    if (argumentsLength === 0) return func;
+
+    return function (argument) {
+        if (argumentsLength > 1) {
+            return curry(func.bind(null, argument));
+        }
+
+        return func(argument);
+    }
+}
+
 describe('problem3 - curry', () => {
     it("returns the same func if it doesn't require any parameters", () => {
         const func = () => 'apple';

tests/problem5.test.js

@@ -27,6 +27,28 @@
         }
 */
 
+class Pipe {
+    constructor(startinValue) {
+        this.startingValue = startinValue;
+    }
+
+    static startingWith (value) {
+        return new Pipe(value);
+    }
+
+    chain (handler) {
+        return new Pipe(handler(this.startingValue));
+    }
+
+    return () {
+        return this.startingValue;
+    }
+
+    finally (handler) {
+        return handler(this.startingValue);
+    }
+}
+
 describe('problem5 - pipe', () => {
     it('returns a wrapped value (an object)', () => {
         expect(Pipe.startingWith(2)).toBeInstanceOf(Pipe);