Think You're a JavaScript Pro? Find Out with this Quiz👇

Q1. How is a forEach statement different from a for statement?

1. Only a for statement uses a callback function.

2. A for statement is generic, but a forEach statement can be used only with an array.

3. Only a forEach statement lets you specify your own iterator.

4. A forEach statement is generic, but a for statement can be used only with an array.

Reference Differences between forEach and for loop

Q2. When would the final statement in the code shown be logged to the console? When would 'results shown' be logged to the console?

let modal = document.querySelector('#result');
setTimeout(function () {
  modal.classList.remove('hidden');
}, 10000);
console.log('Results shown');

1. after 10 second
2. after results are received from the HTTP request
3. after 10000 seconds
4. immediately

Reference Javascript is synchronous and single threaded

Q3. Which snippet could you add to this code to print "food" to the console?

class Animal {
  static belly = [];
  eat() {
    Animal.belly.push('food');
  }
}
let a = new Animal();
a.eat();
console.log(/* Snippet Here */); //Prints food

1. a.prototype.belly[0]
2. Object.getPrototype0f (a).belly[0]
3. Animal.belly[0]
4. a.belly[0]

Reference Javascript Class static Keyword

Q4. You've written the code shown to log a set of consecutive values, but it instead results in the value 5, 5, 5, and 5 being logged to the console. Which revised version of the code would result in the value 1, 2, 3 and 4 being logged?

A

for (var i = 1; i <= 4; i++) {
  setTimeout(function () {
    console.log(i);
  }, i * 10000);
}

B

for (var i = 1; i <= 4; i++) {
  (function (i) {
    setTimeout(function () {
      console.log(j);
    }, j * 1000);
  })(j);
}

C

for (var i = 1; i <= 4; i++) {
  setTimeout(function () {
    console.log(i);
  }, i * 1000);
}

D

for (var i = 1; i <= 4; i++) {
  (function (j) {
    setTimeout(function () {
      console.log(j);
    }, j * 1000);
  })(i);
}

E

for (var j = 1; j <= 4; j++) {
  setTimeout(function () {
    console.log(j);
  }, j * 1000);
}

1. Reference setTimeout
2. Reference immediately invoked anonymous functions

Q5. How does a function create a closure?

1. It reloads the document whenever the value changes.
2. It returns a reference to a variable in its parent scope.
3. It completes execution without returning.
4. It copies a local variable to the global scope.

Reference

Q6. Which statements(multiple options) creates a new function called discountPrice?

A

let discountPrice = function (price) {
  return price * 0.85;
};

B

let discountPrice(price) {
  return price * 0.85;
};

C

let function = discountPrice(price) {
  return price * 0.85;
};

D

discountPrice = function (price) {
  return price * 0.85;
};

Reference defining javascript functions

Q7. What is the result in the console of running the code shown?

var Storm = function () {};
Storm.prototype.precip = 'rain';
var WinterStorm = function () {};
WinterStorm.prototype = new Storm();
WinterStorm.prototype.precip = 'snow';
var bob = new WinterStorm();
console.log(bob.precip);

1. Storm()
2. undefined
3. 'rain'
4. 'snow'

Reference prototype chain

Q8. What is the result in the console of running this code?

'use strict';
function logThis() {
  this.desc = 'logger';
  console.log(this);
}
new logThis();

1. undefined
2. window
3. {desc: "logger"}
4. function

Reference javascript classes

Q9. You're adding error handling to the code shown. Which code would you include within the if statement to specify an error message?

function addNumbers(x, y) {
  if (isNaN(x) || isNaN(y)) {
  }
}

1. exception('One or both parameters are not numbers')
2. catch('One or both parameters are not numbers')
3. error('One or both parameters are not numbers')
4. throw('One or both parameters are not numbers')

Reference javascript throw

Q10. When would you use a conditional statement?

1. When you want to reuse a set of statements multiple times.
2. When you want your code to choose between multiple options.
3. When you want to group data together.
4. When you want to loop through a group of statement.

Reference javascript conditionals

Q11. Which Object method returns an iterable that can be used to iterate over the properties of an object?

1. Object.get()
2. Object.loop()
3. Object.each()
4. Object.keys()

Reference javascript object static methods

Q12. What is one difference between collections created with Map and collections created with Object?

1. You can iterate over values in a Map in their insertion order.
2. You can count the records in a Map with a single method call.
3. Keys in Maps can be strings.
4. You can access values in a Map without iterating over the whole collection.

Reference map methods javascript

Q13. 0 && hi

1. ReferenceError
2. true
3. 0
4. false

Reference boolean logic

Q14. Which of the following values is not a Boolean false?

1. Boolean(0)
2. Boolean("")
3. Boolean(NaN)
4. Boolean("false")

Reference boolean of a string

Q15. For the following class, how do you get the value of 42 from an instance of X?

class X {
  get Y() {
    return 42;
  }
}
var x = new X();

1. x.get('Y')
2. x.Y
3. x.Y()
4. x.get().Y

Reference getters

Post your result in the comment section and let me know how was the quiz🙌👍