CoffeeScript Interview Questions and Answers

npm install --global coffeescript

npm install --save-dev coffeescript

npm install --save-dev @babel/core

npm install --global @babel/core

npm install --save-dev @babel/preset-env  # Or --global for non-project-based usage

square = (x) -> x * x
cube   = (x) -> square(x) * x

var cube, square;
​
square = function(x) {
  return x * x;
};
​
cube = function(x) {
  return square(x) * x;
};​

fill = (container, liquid = "coffee") ->
  "Filling the #{container} with #{liquid}..."

var fill;
​
fill = function(container, liquid = "coffee") {
  return `Filling the ${container} with ${liquid}...`;
};​

###
Fortune Cookie Reader v1.0
Released under the MIT License
###
​
sayFortune = (fortune) ->
  console.log fortune # in bed!
​
/*
Fortune Cookie Reader v1.0
Released under the MIT License
*/
var sayFortune;
​
sayFortune = function(fortune) {
  return console.log(fortune); // in bed!
};

author = "Wittgenstein"
quote  = "A picture is a fact. -- #{ author }"
​
sentence = "#{ 22 / 7 } is a decent approximation of π"

var author, quote, sentence;
​
author = "Wittgenstein";
​
quote = `A picture is a fact. -- ${author}`;
​
sentence = `${22 / 7} is a decent approximation of π`;​

mobyDick = "Call me Ishmael. Some years ago --
  never mind how long precisely -- having little
  or no money in my purse, and nothing particular
  to interest me on shore, I thought I would sail
  about a little and see the watery part of the
  world..."

var mobyDick;
​
mobyDick = "Call me Ishmael. Some years ago -- never mind how long precisely -- having little or no money in my purse, 
and nothing particular to interest me on shore, I thought I would sail about a little and see the watery part of the world...";​

html = """
       <strong>
         cup of coffeescript
       </strong>
       """​

var html;
​
html = `<strong>
  cup of coffeescript
</strong>`;

​Double-quoted block strings, like other double-quoted strings, allow interpolation.

song = ["do", "re", "mi", "fa", "so"]
​
singers = {Jagger: "Rock", Elvis: "Roll"}
​
bitlist = [
  1, 0, 1
  0, 0, 1
  1, 1, 0
]
​
kids =
  brother:
    name: "Max"
    age:  11
  sister:
    name: "Ida"
    age:  9

var bitlist, kids, singers, song;
​
song = ["do", "re", "mi", "fa", "so"];
​
singers = {
  Jagger: "Rock",
  Elvis: "Roll"
};
​
bitlist = [1, 0, 1, 0, 0, 1, 1, 1, 0];
​
kids = {
  brother: {
    name: "Max",
    age: 11
  },
  sister: {
    name: "Ida",
    age: 9
  }
};

name = "Michelangelo"
mask = "orange"
weapon = "nunchuks"
turtle = {name, mask, weapon}
output = "#{turtle.name} wears an #{turtle.mask} mask. Watch out for his #{turtle.weapon}!"

var mask, name, output, turtle, weapon;
​
name = "Michelangelo";
​
mask = "orange";
​
weapon = "nunchuks";
​
turtle = {name, mask, weapon};
​
output = `${turtle.name} wears an ${turtle.mask} mask. Watch out for his ${turtle.weapon}!`;

name = "FtL"
message = " Hello from #{name} "

name = ["sarthak","surabhi", "tejal",
        "dipali", "girija", "devendra"] 

department = {
   id : 10,
   branch : "computer"
}

skills = 
    designer :
         name : "ali"
         surname : "bazzi"
   backend :
         name : "sunny"
          surname : "warner"

engineers = [
  { name : "ali" , surname : "bazzi"},
  { name : "virat" , surname : "sharma"},
  { name : "sharma" , surname : "pandey"},
  { name : "paresh" , surname : "vikramadity"},
  { name : "sandip" , surname : "jain"}
]
   
names_record = engineers.map(firstname) -> firstname.name
console.log(names_record)
Output:

['ali', 'virat', 'sharma', 'paresh', 'sandip'] 

new_string = "Hello how are you "+"Welcome to Free Time Learn".  
console.log new_String  

On compiling the above CoffeeScript code compiler will generate corresponding javascript code as follows :  

// Generated by CoffeeScript 1.10.0  
(function() {  
  var new_string;  
  
  new_string = "Hello how are you " + "Welcome to Interview Questions";  
  
  console.log(new_String);  
  
}).call(this);  

outer = 1
changeNumbers = ->
  inner = -1
  outer = 10
inner = changeNumbers()​

var changeNumbers, inner, outer;
​
outer = 1;
​
changeNumbers = function() {
  var inner;
  inner = -1;
  return outer = 10;
};
​
inner = changeNumbers();​

mood = greatlyImproved if singing
​
if happy and knowsIt
  clapsHands()
  chaChaCha()
else
  showIt()
​
date = if friday then sue else jill

var date, mood;
​
if (singing) {
  mood = greatlyImproved;
}
​
if (happy && knowsIt) {
  clapsHands();
  chaChaCha();
} else {
  showIt();
}
​
date = friday ? sue : jill;

indian_team = (first, second, others...) ->  
  Captain = first  
  WiseCaptain = second  
  team  = others  
  console.log "Captain: " +Captain  
  console.log "Wise captain: " +WiseCaptain  
  console.log "Other team members: " +team  
  
#Passing 4 arguments  
console.log "############## Four Players ############"  
indian_team "Mahendra Singh Dhoni", "Virat Kohli", "Shikhar Dhawan", "Rohit Sharma"  
  
#Passing 6 arguments  
console.log "############## Six Players ############"  
indian_team "Mahendra Singh Dhoni", "Virat Kohli", "Shikhar Dhawan", "Rohit Sharma", "Gurkeerat Singh Mann", "Rishi Dhawan"  
    
#Passing full squad  
console.log "############## Full squad #############"  
indian_team "Mahendra Singh Dhoni", "Virat Kohli", "Shikhar Dhawan", "Rohit Sharma", "Gurkeerat Singh Mann", "Rishi Dhawan", "Ravindra Jadeja", "Axar Patel", "Jasprit Bumrah", "Umesh Yadav", "Harbhajan Singh", "Ashish Nehra", "Hardik Pandya", "Suresh Raina", "Yuvraj Singh", "Ajinkya Rahane"  

# Eat lunch.
eat = (food) -> "#{food} eaten."
eat food for food in ['toast', 'cheese', 'wine']
​
# Fine five course dining.
courses = ['greens', 'caviar', 'truffles', 'roast', 'cake']
menu = (i, dish) -> "Menu Item #{i}: #{dish}" 
menu i + 1, dish for dish, i in courses
​
# Health conscious meal.
foods = ['broccoli', 'spinach', 'chocolate']
eat food for food in foods when food isnt 'chocolate'

// Eat lunch.
var courses, dish, eat, food, foods, i, j, k, l, len, len1, len2, menu, ref;
​
eat = function(food) {
  return `${food} eaten.`;
};
​
ref = ['toast', 'cheese', 'wine'];
for (j = 0, len = ref.length; j < len; j++) {
  food = ref[j];
  eat(food);
}
​
// Fine five course dining.
courses = ['greens', 'caviar', 'truffles', 'roast', 'cake'];
​
menu = function(i, dish) {
  return `Menu Item ${i}: ${dish}`;
};
​
for (i = k = 0, len1 = courses.length; k < len1; i = ++k) {
  dish = courses[i];
  menu(i + 1, dish);
}
​
// Health conscious meal.
foods = ['broccoli', 'spinach', 'chocolate'];
​
for (l = 0, len2 = foods.length; l < len2; l++) {
  food = foods[l];
  if (food !== 'chocolate') {
    eat(food);
  }
}​

shortNames = (name for name in list when name.length < 5)

indian_team = (first, second, others...., last) ->  
  Captain = first  
  WiseCaptain = second  
  team  = others  
  Wicketkeeper =last  
  console.log "Captain: " +Captain  
  console.log "Wise captain: " +WiseCaptain  
  console.log "Wicket keeper is:"+last  
  console.log "Other team members: " +team    
    
squad = [  
   "Mahendra Singh Dhoni"  
   "Virat Kohli"  
   "Shikhar Dhawan"  
   "Rohit Sharma"     
   "Gurkeerat Singh Mann"  
   "Rishi Dhawan"  
   "R Ashwin"  
   "Ravindra Jadeja"  
   "Axar Patel"  
   "Jasprit Bumrah"  
   "Umesh Yadav"  
   "Harbhajan Singh"  
   "Ashish Nehra"  
   "Hardik Pandya"  
   "Suresh Raina"  
   "Yuvraj Singh"  
   "Ajinkya Rahane"  
 ]​

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]
​
start   = numbers[0..2]
​
middle  = numbers[3...-2]
​
end     = numbers[-2..]
​
copy    = numbers[..]​

var copy, end, middle, numbers, start;
​
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9];
​
start = numbers.slice(0, 3);
​
middle = numbers.slice(3, -2);
​
end = numbers.slice(-2);
​
copy = numbers.slice(0);​

numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
​
numbers[3..6] = [-3, -4, -5, -6]​

var numbers, ref,
  splice = [].splice;
​
numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
​
splice.apply(numbers, [3, 4].concat(ref = [-3, -4, -5, -6])), ref;

Note that JavaScript strings are immutable, and can’t be spliced.

-7 % 5 == -2 # The remainder of 7 / 5
-7 %% 5 == 3 # n %% 5 is always between 0 and 4
​
tabs.selectTabAtIndex((tabs.currentIndex - count) %% tabs.length)

var modulo = function(a, b) { return (+a % (b = +b) + b) % b; };
​
-7 % 5 === -2; // The remainder of 7 / 5
​
modulo(-7, 5) === 3; // n %% 5 is always between 0 and 4
​
tabs.selectTabAtIndex(modulo(tabs.currentIndex - count, tabs.length));​

All together now : 

# Your browser must support async/await and speech synthesis
# to run this example.
sleep = (ms) ->
  new Promise (resolve) ->
    window.setTimeout resolve, ms
​
say = (text) ->
  window.speechSynthesis.cancel()
  window.speechSynthesis.speak new SpeechSynthesisUtterance text
​
countdown = (seconds) ->
  for i in [seconds..1]
    say i
    await sleep 1000 # wait one second
  say "Blastoff!"
​
countdown 3​

// Your browser must support async/await and speech synthesis
// to run this example.
var countdown, say, sleep;
​
sleep = function(ms) {
  return new Promise(function(resolve) {
    return window.setTimeout(resolve, ms);
  });
};
​
say = function(text) {
  window.speechSynthesis.cancel();
  return window.speechSynthesis.speak(new SpeechSynthesisUtterance(text));
};
​
countdown = async function(seconds) {
  var i, j, ref;
  for (i = j = ref = seconds; (ref <= 1 ? j <= 1 : j >= 1); i = ref <= 1 ? ++j : --j) {
    say(i);
    await sleep(1000); // wait one second
  }
  return say("Blastoff!");
};
​
countdown(3);

class Animal
  constructor: (@name) ->
​
  move: (meters) ->
    alert @name + " moved #{meters}m."
​
class Snake extends Animal
  move: ->
    alert "Slithering..."
    super 5
​
class Horse extends Animal
  move: ->
    alert "Galloping..."
    super 45
​
sam = new Snake "Sammy the Python"
tom = new Horse "Tommy the Palomino"
​
sam.move()
tom.move()

var Animal, Horse, Snake, sam, tom;
​
Animal = class Animal {
  constructor(name) {
    this.name = name;
  }
​
  move(meters) {
    return alert(this.name + ` moved ${meters}m.`);
  }
​
};
​
Snake = class Snake extends Animal {
  move() {
    alert("Slithering...");
    return super.move(5);
  }
​
};
​
Horse = class Horse extends Animal {
  move() {
    alert("Galloping...");
    return super.move(45);
  }
​
};
​
sam = new Snake("Sammy the Python");
​
tom = new Horse("Tommy the Palomino");
​
sam.move();
​
tom.move();​

class Teenager
  @say: (speech) ->
    words = speech.split ' '
    fillers = ['uh', 'um', 'like', 'actually', 'so', 'maybe']
    output = []
    for word, index in words
      output.push word
      output.push fillers[Math.floor(Math.random() * fillers.length)] unless index is words.length - 1
    output.join ', '
​
var Teenager;
​
Teenager = class Teenager {
  static say(speech) {
    var fillers, i, index, len, output, word, words;
    words = speech.split(' ');
    fillers = ['uh', 'um', 'like', 'actually', 'so', 'maybe'];
    output = [];
    for (index = i = 0, len = words.length; i < len; index = ++i) {
      word = words[index];
      output.push(word);
      if (index !== words.length - 1) {
        output.push(fillers[Math.floor(Math.random() * fillers.length)]);
      }
    }
    return output.join(', ');
  }
​
};​

String::dasherize = ->
  this.replace /_/g, "-"
​
String.prototype.dasherize = function() {
  return this.replace(/_/g, "-");
};

switch day
  when "Mon" then go work
  when "Tue" then go relax
  when "Thu" then go iceFishing
  when "Fri", "Sat"
    if day is bingoDay
      go bingo
      go dancing
  when "Sun" then go church
  else go work
​
switch (day) {
  case "Mon":
    go(work);
    break;
  case "Tue":
    go(relax);
    break;
  case "Thu":
    go(iceFishing);
    break;
  case "Fri":
  case "Sat":
    if (day === bingoDay) {
      go(bingo);
      go(dancing);
    }
    break;
  case "Sun":
    go(church);
    break;
  default:
    go(work);
}​

score = 76
grade = switch
  when score < 60 then 'F'
  when score < 70 then 'D'
  when score < 80 then 'C'
  when score < 90 then 'B'
  else 'A'
# grade == 'C'
​
var grade, score;
​
score = 76;
​
grade = (function() {
  switch (false) {
    case !(score < 60):
      return 'F';
    case !(score < 70):
      return 'D';
    case !(score < 80):
      return 'C';
    case !(score < 90):
      return 'B';
    default:
      return 'A';
  }
})();
​
// grade == 'C'

try
  allHellBreaksLoose()
  catsAndDogsLivingTogether()
catch error
  print error
finally
  cleanUp()
​
var error;
​
try {
  allHellBreaksLoose();
  catsAndDogsLivingTogether();
} catch (error1) {
  error = error1;
  print(error);
} finally {
  cleanUp();
}

NUMBER     = ///
  ^ 0b[01]+    |              # binary
  ^ 0o[0-7]+   |              # octal
  ^ 0x[\da-f]+ |              # hex
  ^ \d*\.?\d+ (?:e[+-]?\d+)?  # decimal
///i
​
var NUMBER;
​
NUMBER = /^0b[01]+|^0o[0-7]+|^0x[\da-f]+|^\d*\.?\d+(?:e[+-]?\d+)?/i; // binary
// octal
// hex
// decimal

import './local-file.js' # Must be the filename of the generated file
import 'package'
​
import _ from 'underscore'
import * as underscore from 'underscore'
​
import { now } from 'underscore'
import { now as currentTimestamp } from 'underscore'
import { first, last } from 'underscore'
import utilityBelt, { each } from 'underscore'
​
import dates from './calendar.json' assert { type: 'json' }
​
export default Math
export square = (x) -> x * x
export class Mathematics
  least: (x, y) -> if x < y then x else y
​
export { sqrt }
export { sqrt as squareRoot }
export { Mathematics as default, sqrt as squareRoot }
​
export * from 'underscore'
export { max, min } from 'underscore'
export { version } from './package.json' assert { type: 'json' }

import './local-file.js';
​
import 'package';
​
import _ from 'underscore';
​
import * as underscore from 'underscore';
​
import {
  now
} from 'underscore';
​
import {
  now as currentTimestamp
} from 'underscore';
​
import {
  first,
  last
} from 'underscore';
​
import utilityBelt, {
  each
} from 'underscore';
​
import dates from './calendar.json' assert {
  type: 'json'
};
​
export default Math;
​
export var square = function(x) {
  return x * x;
};
​
export var Mathematics = class Mathematics {
  least(x, y) {
    if (x < y) {
      return x;
    } else {
      return y;
    }
  }
​
};
​
export {
  sqrt
};
​
export {
  sqrt as squareRoot
};
​
export {
  Mathematics as default,
  sqrt as squareRoot
};
​
export * from 'underscore';
​
export {
  max,
  min
} from 'underscore';
​
export {
  version
} from './package.json' assert {
    type: 'json'
  };

# Your browser must support dynamic import to run this example.
​
do ->
  { run } = await import('./browser-compiler-modern/coffeescript.js')
  run '''
    if 5 < new Date().getHours() < 9
      alert 'Time to make the coffee!'
    else
      alert 'Time to get some work done.'
  '''

// Your browser must support dynamic import to run this example.
(async function() {
  var run;
  ({run} = (await import('./browser-compiler-modern/coffeescript.js')));
  return run(`if 5 < new Date().getHours() < 9
  alert 'Time to make the coffee!'
else
  alert 'Time to get some work done.'`);
})();

hi = `function() {
  return [document.title, "Hello JavaScript"].join(": ");
}`
​
var hi;
​
hi = function() {
  return [document.title, "Hello JavaScript"].join(": ");
};

markdown = `function () {
  return \`In Markdown, write code like \\\`this\\\`\`;
}`
​
var markdown;
​
markdown = function () {
  return `In Markdown, write code like \`this\``;
};​

```
function time() {
  return `The time is ${new Date().toLocaleTimeString()}`;
}
```
​
function time() {
  return `The time is ${new Date().toLocaleTimeString()}`;
}
;

renderStarRating = ({ rating, maxStars }) ->
  <aside title={"Rating: #{rating} of #{maxStars} stars"}>
    {for wholeStar in [0...Math.floor(rating)]
      <Star className="wholeStar" key={wholeStar} />}
    {if rating % 1 isnt 0
      <Star className="halfStar" />}
    {for emptyStar in [Math.ceil(rating)...maxStars]
      <Star className="emptyStar" key={emptyStar} />}
  </aside>
​
var renderStarRating;
​
renderStarRating = function({rating, maxStars}) {
  var emptyStar, wholeStar;
  return <aside title={`Rating: ${rating} of ${maxStars} stars`}>
    {(function() {
    var i, ref, results;
    results = [];
    for (wholeStar = i = 0, ref = Math.floor(rating); (0 <= ref ? i < ref : i > ref); wholeStar = 0 <= ref ? ++i : --i) {
      results.push(<Star className="wholeStar" key={wholeStar} />);
    }
    return results;
  })()}
    {rating % 1 !== 0 ? <Star className="halfStar" /> : void 0}
    {(function() {
    var i, ref, ref1, results;
    results = [];
    for (emptyStar = i = ref = Math.ceil(rating), ref1 = maxStars; (ref <= ref1 ? i < ref1 : i > ref1); emptyStar = ref <= ref1 ? ++i : --i) {
      results.push(<Star className="emptyStar" key={emptyStar} />);
    }
    return results;
  })()}
  </aside>;
};