Workshop 1

Setup

npm i

Usage

npm run start

Working on the task

Try to use TDD for the development (first tests, then implementation)

1. For every task create a file with the implementation of the function and single export
2. Add a separate file with tests for the task using https://jestjs.io/

Sum of array

Write a function that finds a sum of array items.

Input: array of numbers Output: number (sum of numbers)

f1

Merges two objects, but it doesn't affect the properties that are already defined. Right objects are merged to the left

Example

f1({ a: 1, b: 2 }, { b: 3, c: 4 })
// { a: 1, b: 2, c:4 }

f1 (multiple sources)

Extend the f1 function to support multiple sources.

Example

f1({ a: 1, b: 2 }, { b: 3, c: 4 }, { a: 0: b: 4, d: 5, })
// { a: 1, b: 2, c:4, d: 5 }

f1 (deep merge)

Extend the f1 function to support deep operations.

Example

f1({ a: { b: 2 } }, { a: { b: 1, c: 3 } });
// { a: { b: 2, c: 3 } }

f2

Find difference of two arrays. The function should return a new array that includes items that are presented in the left array, but not presented in the right array. Order is determined by the first array.

Example

f2([2, 1, 3], [2, 3, 4]);
// [1]

f3

Find intersection of two arrays. The function should return a new array that includes items that are presented both in the left and right arrays. Order is determined by the first array.

f3([2, 1, 3], [2, 3, 4]);
// [2, 3]

f4

Gets the value at path of object. If the path does not exist in the object then undefined should be returned path is a string of keys with . as a delimiter.

Example,

const object = { 'a': { 'b': { 'c': 3 } } };
 
f4(object, 'a.b.c');
// 3

f4(object, 'a.b.c.d.e');
// undefined

f5

Sets the value at path of object. If the path does not exist in the object then it should be recursively created. path is a string of keys with . as a delimiter.

Example,

const object = { 'a': { 'b': { 'c': 3 } } };
 
f5(object, 'a.b.c', 5);
// { a: { b: { c: 5 } } };

f5(object, 'a.b.c.d.e', 10);
// { a: { b: { c: { d: { e: 10 } } } } };

rename keys

function that recursively renames keys and returns a new modified object.

1st argument has an object that has to be changed 2nd argument has an object of key-values, where keys are the keys that should be renamed and the values are the resulting key name

if the key already exists, then the old value is replaced with the new one

Example,

renameKeys({ 'a': { 'b': { 'c': 5 } } }, { c: 'b' })
// { 'a': { 'b': { 'b': 5 } } };

renameKeys({ 'a': { 'b': { 'c': 5 }, c: { d: 6 } } }, { c: 'b' })
// { 'a': { 'b': { 'd': 6 } } };

time stamper

write a function that accepts 0 params. when you invoke the function it adds a timestamp value to the array (new Date().getTime()) and returns the array. So every new invocation should memoize previous array state and return the new array with the new time stamp NOTE: there should be no global variables outside of the function

For example,

invocation 1:

timestamper()
// [1570641110947]

invocation 2:

timestamper()
// [1570641110947, 1570641136368]

invocation 3:

timestamper()
// [1570641110947, 1570641136368, 1570641148449]