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BasicJS

⚠️ DO NOT SUBMIT PULL REQUESTS TO THIS REPO ⚠️

General task description

Your task is to write several functions that are the solution to the subtasks. Subtasks descriptions, as well as instructions on how to run tests and submit solutions are below.

Count cats!

Your task is to count the cats hidden in the backyard (presented by two-dimensional Array). Cats hide well, but their ears ("^^") are clearly visible. Your task is to implement the countCats(backyard) function that will count cats. Good luck!

Number of cats found should be number. If no cats found, function should return 0.

Write your code in src/count-cats.js.

Carbon dating

To determine the age of archaeological finds, radioisotope dating is widely used. One of its types is radiocarbon dating.

The approximate age of the sample is calculated by measuring the ratio of the modern activity of the C14 isotope to the activity of the same isotope in the sample.

Read about method

Your task is to implement the function dateSample(sampleActivity) that calculates sample approximate age (in years). Please use given MODERN_ACTIVITY and HALF_LIFE_PERIOD.

Function parameter sampleActivity is a string. Calculated sample age must be number. Age must be integer. Age must be rounded up. In case of wrong input parameter type or inadequate activity value or absence of argument function must return false.

Write your code in src/carbon-dating.js.

Dream team

Imagine you and your friends decide to create a dream team. This team should have a cool secret name that contains encrypted information about it. For example, these may be the first letters of the names of its members in upper case sorted alphabetically. Your task is to implement the createDreamTeam(members) function that returns name of a newly made team (string) based on the names of its members (Array). Good luck!

Names of the members should be strings. Values with other type should be ignored. In case of wrong members type function must return false.

NB! Team member name may contain whitespaces.

For example:

createDreamTeam(['Matt', 'Ann', 'Dmitry', 'Max']) => 'ADMM'

createDreamTeam(['Olivia', 1111, 'Lily', 'Oscar', true, null]) => 'LOO'

Write your code in src/dream-team.js.

What season?

Your task is to implement the function getSeason(date) that accepts Date object and returns the time of the year that matches it. Time of the year must be string.

If the date argument was not passed, the function must return the string 'Unable to determine the time of year!'. If the date argument is invalid, the function must throw an Error.

Shh! An enemy scout has lurked among the arguments that come into this function.

Disguised

He is guided by the famous proverb: “If it looks like a duck, swims like a duck and quacks like a duck, then it probably is a duck (who cares what it really is)”. He is expertly disguised as a real date, but a clever javascript developer can catch him and throw an Error just in time!

Write your code in src/what-season.js.

Tower of Hanoi

Tower of hanoi visualisation

Tower of Hanoi is famous mathematical puzzle of the 18th century. It consists of three rods and a number of disks of different sizes, which can slide onto any rod. The puzzle starts with the disks in a neat stack in ascending order of size on one rod, the smallest at the top, thus making a conical shape.

The objective of the puzzle is to move the entire stack to another rod, obeying the following simple rules:

  • Only one disk can be moved at a time.
  • Each move consists of taking the upper disk from one of the stacks and placing it on top of another stack or on an empty rod.
  • No larger disk may be placed on top of a smaller disk.

Your task is much easier than coming up with an algorithm that solves this puzzle :)

Implement the function calculateHanoi that accepts diskNumber and turnsSpeed parameters. diskNumber is a number of disks and turnsSpeed is the speed of moving discs (in turns per hour). Both parameters are numbers.

calculateHanoi function returns an object with 2 properties:

  • turns (minimum number of turns to solve the puzzle)
  • seconds (minimum number of seconds to solve the puzzle at a given turnsSpeed).

You don't need to validate parameters.

Write your code in src/hanoi-tower.js.

Transform array

Your task is to implement the function transform(arr) that takes an array and returns it transformed, based on the control sequences that it contains. Control sequences are defined string elements of the mentioned array:

  • --discard-next excludes the next element of the array from the transformed array.
  • --discard-prev excludes the previous element of the array from the transformed array.
  • --double-next doubles the next element of the array in the transformed array.
  • --double-prev doubles the previous element of the array in the transformed array.

For example:

transform([1, 2, 3, '--double-next', 4, 5]) => [1, 2, 3, 4, 4, 5]

transform([1, 2, 3, '--discard-prev', 4, 5]) => [1, 2, 4, 5]

Control sequences do not fall into the transformed array. Control sequences in initial array do not occur in a row. If there is no element next to the control sequence to which it can be applied, it does nothing. The function should throw an Error if the arr is not an Array.

Write your code in src/transform-array.js.

Chain maker

Let's practice in chaining!

Your task is to create the object chainMaker that creates chains. The finished chain is a string and looks like this: '( value1 )~~( value2 )~~( value3 )'. The chainMaker has several methods for creating chains and modifying them:

  • getLength returns the current chain length as a number;
  • addLink(value) adds a link containing a string representation of the value to the chain;
  • removeLink(position) removes a chain link in the specified position;
  • reverseChain reverses the chain;
  • finishChain ends the chain and returns it.

addLink, reverseChain and removeLink methods are chainable, while the another ones are not. If addLink is called with no arguments, it adds an empty link ('( )') to the chain. If removeLink accepts invalid position (e.g. not a number, or a fractional number, or corresponding to a nonexistent link), it must throw an Error. After calling the finishChain method, the existing chain must be deleted, as if an Error was thrown.

For example:

chainMaker.addLink(1).addLink(2).addLink(3).finishChain() => '( 1 )~~( 2 )~~( 3 )'

chainMaker.addLink(1).addLink(2).removeLink(1).addLink(3).finishChain() => '( 2 )~~( 3 )'

chainMaker.addLink(1).addLink(2).reverseChain().addLink(3).finishChain() => '( 2 )~~( 1 )~~( 3 )'

Write your code in src/simple-chain.js.

Recursive depth calculator

Go deeper

Your task is to implement the class DepthCalculator with method calculateDepth that takes an array and returns its depth.

calculateDepth method must pass the given array recursively. Depth of a flat array is 1. Method must correctly work with arrays that contain no elements or contain empty arrays.

For example:

const depthCalc = new DepthCalculator(); const { calculateDepth } = depthCalc;

calculateDepth([1, 2, 3, 4, 5]) => 1

calculateDepth([1, 2, 3, [4, 5]]) => 2

calculateDepth([[[]]]) => 3

Write your code in src/recursive-depth.js.

Extended repeater

Your task is to implement the function repeater(str, options). This function returns a repeating string based on the given parameters:

  • str is a string to repeat;
  • options is an object of options, that contains properties:
    • repeatTimes sets the number of repetitions of the str;
    • separator is a string separating repetitions of the str;
    • addition is an additional string that will be added to each repetition of the str;
    • additionRepeatTimes sets the number of repetitions of the addition;
    • additionSeparator is a string separating repetitions of the addition.

The str and addition parameters are strings by default. In case when type of these parameters is different, they must be converted to a string.

separator and additionSeparator parameters are strings.

repeatTimes and additionRepeatTimes are integer numbers (in the absence of any of them, the corresponding string is not repeated).

The only indispensable parameter is str, any others may be not defined. separator default value is '+'. additionSeparator default value is '|'.

For example: repeater('STRING', { repeatTimes: 3, separator: '**', addition: 'PLUS', additionRepeatTimes: 3, additionSeparator: '00' }) => 'STRINGPLUS00PLUS00PLUS**STRINGPLUS00PLUS00PLUS**STRINGPLUS00PLUS00PLUS'

Write your code in src/extended-repeater.js.

Vigenere cipher

Cryptography is awesome! Let's try to organize production of encryption machines. Our machines will use one of the encryption methods that are easy to understand, but also not amenable to simple cryptanalysis - the Vigenere cipher.

Our machine will have 2 modifications: direct and reverse (the type of machine is determined at the moment of creation). The direct machine simply encodes and decodes the string that was transmitted to it, and the reverse machine returns an inverted string after encoding and decoding.

Your task is to implement the class VigenereCipheringMachine. constructor of this class accepts true (or nothing) to create direct machine and false to create reverse machine. Each instance of VigenereCipheringMachine must have 2 methods: encrypt and decrypt.

encrypt method accepts 2 parameters: message (string to encode) and key (string-keyword).

decrypt method accepts 2 parameters: encryptedMessage (string to decode) and key (string-keyword).

These parameters for both methods are mandatory. If at least one of them has not been given, an Error must be thrown.

You don't need to validate value sent to constructor and to encrypt and decrypt methods (except throwing an Error on absence of argument for these methods).

Write your code in src/vigenere-cipher.js.

Prerequisites

  1. Install Node.js
  2. Fork this repository: https://github.com/AlreadyBored/basic-js
  3. Clone your newly created repo: https://github.com/<%your_github_username%>/basic-js/
  4. Go to folder basic-js
  5. To install all dependencies use npm install
  6. Run npm run test in command line.
  7. You will see the number of passing and failing tests. 100% of passing tests is equal to 100p in score

Submit to rs app

  1. Open rs app and login
  2. Go to submit task page
  3. Select your task (BasicJS)
  4. Press the submit button and enjoy

Notes

  1. We recommend you to use nodejs of version 10 or lower. If you use any of features, that does not supported by node v10, score won't be submitted.
  2. Please, be sure that each of your tests is limited to 30 sec.

© AlreadyBored

& Thanks mikhama for assistance!