JavaScript Functions and Scope Quiz

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Question 1/15

What does the following code return? 
function testScope() {
  console.log(a);
  var a = 5;
  return a;
}

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Question 2/15

What will be returned by the arrow function in the following code? 
let add = (a, b) => a + b;
let result = add(3, 4);

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Question 3/15

What will the function `returnSum` return when called with no arguments? 
function returnSum(a = 1, b = 1) {
  return a + b;
}

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Question 4/15

Given the function declaration, which option correctly calls the function with 3 as an argument? 
function printNumber(n) {
  console.log(n);
}

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Question 5/15

What value will the variable `result` hold? 
function multiplier(a, b = 2) {
  return a * b;
}
let result = multiplier(4);

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Question 6/15

What will the following code log in the console? 
let car = {
  make: 'Toyota',
  year: 2019,
};
car.getAge = function() {
  const currentYear = new Date().getFullYear();
  return currentYear - this.year;
};
console.log(car.getAge());

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Question 7/15

What is the impact of calling `comparison(5, '5')` in this code? 
function comparison(x, y) {
  return x == y;
}

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Question 8/15

What will be the output of this immediately invoked function expression? 
(function() {
  var a = b = 5;
})();
console.log(typeof a);
console.log(typeof b);

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Question 9/15

Consider the below code. What will be logged to the console? 
let y = 10;
function modifyVariable() {
  y += 5;
  console.log(y);
}
modifyVariable();

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Question 10/15

What does the following function return when called with argument 5? 
function increment(x) {
  return ++x;
}

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Question 11/15

What will be logged after running the following code? 
function logger(x = 'default') {
  console.log(x);
}
logger();

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Question 12/15

In the code snippet below, what is the value of result? 
function square(x) {
  return x * x;
}
let result = square(3) + square(4);

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Question 13/15

In the following code, what will `greet()` log to the console? 
function greet() {
  console.log(message);
  var message = 'Hello, World!';
}

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Question 14/15

For this code, what is returned by `compute()`? 
function compute() {
  let a = 3;
  let b = 4;
  return a + b;
}

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Question 15/15

Which statement is correct about the `outerFunction` in this code? 
function outerFunction() {
  var x = 'outer-local';
  function innerFunction() {
    var x = 'inner-local';
    console.log(x);
  }
  innerFunction();
}
outerFunction();

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Your Answers

Question 1/15
😊 Your answer was correct 🙁 Your answer was incorrect
What does the following code return? 
function testScope() {
  console.log(a);
  var a = 5;
  return a;
}

Available answers

Due to JavaScript's hoisting, the variable `a` is hoisted to the top of the function with an initial value of `undefined`. Thus, console.log(a) prints `undefined` before `a` is assigned to 5.
Question 2/15
😊 Your answer was correct 🙁 Your answer was incorrect
What will be returned by the arrow function in the following code? 
let add = (a, b) => a + b;
let result = add(3, 4);

Available answers

The arrow function add takes two arguments and returns their sum. When called with 3 and 4, it returns 7.
Question 3/15
😊 Your answer was correct 🙁 Your answer was incorrect
What will the function `returnSum` return when called with no arguments? 
function returnSum(a = 1, b = 1) {
  return a + b;
}

Available answers

Both parameters have default values of 1. If called with no arguments, `returnSum` returns 1 + 1, which is 2.
Question 4/15
😊 Your answer was correct 🙁 Your answer was incorrect
Given the function declaration, which option correctly calls the function with 3 as an argument? 
function printNumber(n) {
  console.log(n);
}

Available answers

`printNumber(3);` correctly calls the function with 3 as an argument. The other options are either incorrect syntax or misassignments.
Question 5/15
😊 Your answer was correct 🙁 Your answer was incorrect
What value will the variable `result` hold? 
function multiplier(a, b = 2) {
  return a * b;
}
let result = multiplier(4);

Available answers

The function `multiplier` defaults `b` to 2 if not provided. The call `multiplier(4)` is thus 4 * 2, resulting in 8.
Question 6/15
😊 Your answer was correct 🙁 Your answer was incorrect
What will the following code log in the console? 
let car = {
  make: 'Toyota',
  year: 2019,
};
car.getAge = function() {
  const currentYear = new Date().getFullYear();
  return currentYear - this.year;
};
console.log(car.getAge());

Available answers

`car.getAge` method calculates and returns the difference between the current year and the car's manufacture year, 2019.
Question 7/15
😊 Your answer was correct 🙁 Your answer was incorrect
What is the impact of calling `comparison(5, '5')` in this code? 
function comparison(x, y) {
  return x == y;
}

Available answers

The loose equality `==` allows type coercion, so `comparison(5, '5')` evaluates to true.
Question 8/15
😊 Your answer was correct 🙁 Your answer was incorrect
What will be the output of this immediately invoked function expression? 
(function() {
  var a = b = 5;
})();
console.log(typeof a);
console.log(typeof b);

Available answers

In the IIFE, `b` is assigned to 5 in the global scope because it's not declared with var, let, or const. `a` is only defined within the function's scope, so it is undefined outside. The console logs 'undefined' and 'number'.
Question 9/15
😊 Your answer was correct 🙁 Your answer was incorrect
Consider the below code. What will be logged to the console? 
let y = 10;
function modifyVariable() {
  y += 5;
  console.log(y);
}
modifyVariable();

Available answers

Since y is declared outside the function with a value of 10, and the function modifyVariable adds 5 to y, the logged value will be 15.
Question 10/15
😊 Your answer was correct 🙁 Your answer was incorrect
What does the following function return when called with argument 5? 
function increment(x) {
  return ++x;
}

Available answers

The function uses the prefix increment operator, which increases the value of x by one before the value is returned. So, calling increment(5) returns 6.
Question 11/15
😊 Your answer was correct 🙁 Your answer was incorrect
What will be logged after running the following code? 
function logger(x = 'default') {
  console.log(x);
}
logger();

Available answers

Function `logger` is called without arguments, making `x` default to 'default', which is logged.
Question 12/15
😊 Your answer was correct 🙁 Your answer was incorrect
In the code snippet below, what is the value of result? 
function square(x) {
  return x * x;
}
let result = square(3) + square(4);

Available answers

The function square returns the square of its argument. Thus, square(3) returns 9 and square(4) returns 16. Hence, result is 9 + 16, which is 25.
Question 13/15
😊 Your answer was correct 🙁 Your answer was incorrect
In the following code, what will `greet()` log to the console? 
function greet() {
  console.log(message);
  var message = 'Hello, World!';
}

Available answers

Due to hoisting, the variable `message` is declared at the top of the function but not initialized. Thus, `console.log(message)` prints `undefined`.
Question 14/15
😊 Your answer was correct 🙁 Your answer was incorrect
For this code, what is returned by `compute()`? 
function compute() {
  let a = 3;
  let b = 4;
  return a + b;
}

Available answers

`compute` evaluates the sum of `a` and `b`, which is 3 + 4, resulting in 7.
Question 15/15
😊 Your answer was correct 🙁 Your answer was incorrect
Which statement is correct about the `outerFunction` in this code? 
function outerFunction() {
  var x = 'outer-local';
  function innerFunction() {
    var x = 'inner-local';
    console.log(x);
  }
  innerFunction();
}
outerFunction();

Available answers

`innerFunction` accesses its own local variable `x` which is 'inner-local'. Thus, `outerFunction` logs 'inner-local'.