I had a fascinating experience when I reached out to ChatGPT for mind twister puzzles. As someone who enjoys a good mental challenge, I was thoroughly intrigued by the puzzles that were presented to me. Some of the puzzles were particularly perplexing and left me feeling utterly confused, but this only served to make the experience more thrilling. Overall, I was grateful for the opportunity to exercise my cognitive abilities and engage in a mentally stimulating activity.

I have organized the puzzles, complete with answers and explanations for each one. With a link at the end of every Question and Answer, readers can easily navigate. I hope that this blog post will be a valuable resource for those who enjoy mental challenges and provide a good read.

📢 Let's begin...

1. What is the output of the following code snippet?

a: console.log(1 + "2" + "2");
b: console.log(1 + +"2" + "2");
c: console.log(1 + -"1" + "2");
d: console.log(+"1" + "1" + "2");
e: console.log("A" - "B" + "2");
f: console.log("A" - "B" + 2);

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• Answer a - Answer b
• Answer c - Answer d
• Answer e - Answer f

2. What is the output of the following code snippet?

for (var i = 0; i < 5; i++) {
  setTimeout(() => console.log(i), 100);
}

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• Answer

3. What is the output of the following code snippet?

const a = {b: 1};
const b = {c: 2};
const c = {...a, ...b};
console.log(c);

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• Answer

4. What is the output of the following code snippet?

const a = [1, 2, 3];
const b = [1, 2, 3];
const c = "1,2,3";
console.log(a == c);
console.log(b == c);
console.log(a == b);

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• Answer

5. What is the output of the following code snippet?

function a (){
  return arguments;
} 
console.log(a(1, 2, 3));

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• Answer

6. What is the output of the following code snippet?

const a = [1, 2, 3];
a[10] = 10;
a: console.log(a);
b: console.log(a.length);

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• Answer

7. What is the output of the following code snippet?

const a = [1, 2, 3];
a[-1] = 0;
console.log(a);
console.log(a.length);

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• Answer

8. What is the output of the following code snippet?

const a = {a: 1, b: 2};
const b = {b: 3, c: 4};
const c = {...a, ...b};
console.log(c);

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• Answer

9. What is the output of the following code snippet?

console.log(typeof NaN);
console.log(NaN == NaN);
console.log(NaN === NaN);

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• Answer

10. What is the output of the following code snippet?

const a = "hello";
a.toUpperCase();
console.log(a);

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• Answer

Answers:-

• Note `In JavaScript, the + operator is used for both addition and string concatenation. When you use the + operator with a number and a string, JavaScript converts the number to a string and then concatenates the two strings together.

Answer 1 a

• In the expression 1 + "2" + "2", the first + operator is between a number (1) and a string ("2"), so JavaScript converts the number to a string and concatenates it with the string "2". The result of this operation is the string "12".
• The second + operator is between two strings ("12" and "2"), so JavaScript simply concatenates them together, resulting in the string "122".
• Therefore, the output of the code console.log(1 + "2" + "2"); would be "122".

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Question 1

Answer 1 b

• In the expression +"2", the + operator is used as a unary operator on the string "2". Since the string "2" can be converted to a number, the result of this operation is the number 2.
• Therefore, the expression 1 + +"2" + "2" can be rewritten as 1 + 2 + "2".
• The first + operator is between a number (1) and a number (2), so JavaScript adds them together, resulting in the number 3.
• The second + operator is between a number (3) and a string ("2"), so JavaScript converts the number 3 to a string and concatenates it with the string "2". The result of this operation is the string "32".
• Therefore, the output of the code console.log(1 + +"2" + "2"); would be "32".

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Question 1

Answer 1 c

• In the expression - "1", the - operator is used as a unary operator on the string "1". Since the string "1" can be converted to a number, the result of this operation is the number -1.
• Therefore, the expression 1 + -"1" + "2" can be rewritten as 1 + (-1) + "2".
• The first + operator is between a number (1) and a number (-1), so JavaScript adds them together, resulting in the number 0.
• The second + operator is between a number (0) and a string ("2"), so JavaScript converts the number 0 to a string and concatenates it with the string "2". The result of this operation is the string "02".
• Therefore, the output of the code console.log(1 + -"1" + "2"); would be "02".

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Question 1

Answer 1 d

• In the expression +"1", the + operator is used as a unary operator on the string "1". Since the string "1" can be converted to a number, the result of this operation is the number 1.
• Therefore, the expression +"1" + "1" + "2" can be rewritten as 1 + "1" + "2".
• The first + operator is between a number (1) and a string ("1"), so JavaScript converts the number 1 to a string and concatenates it with the string "1". The result of this operation is the string "11".
• The second + operator is between a string ("11") and a string ("2"), so JavaScript concatenates them together, resulting in the string "112".
• Therefore, the output of the code console.log(+"1" + "1" + "2"); would be "112".

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Question 1

Answer 1 e

• In JavaScript, the - operator is used for subtraction between two numbers. When you use the - operator with a string, JavaScript tries to convert the string to a number.
• In the expression "A" - "B", JavaScript tries to subtract the numbers represented by the strings "A" and "B". However, since these strings cannot be converted to numbers, the result of this operation is NaN (Not a Number).
• Therefore, the expression "A" - "B" + "2" can be rewritten as NaN + "2".
• The + operator is between NaN and a string ("2"), so JavaScript converts NaN to the string "NaN" and concatenates it with the string "2". The result of this operation is the string "NaN2".
• Therefore, the output of the code console.log("A" - "B" + "2"); would be "NaN2".

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Question 1

Answer 1 f

• In the expression "A" - "B", JavaScript tries to subtract the numbers represented by the strings "A" and "B". However, since these strings cannot be converted to numbers, the result of this operation is NaN (Not a Number).
• Therefore, the expression "A" - "B" + 2 can be rewritten as NaN + 2.
• The + operator is between NaN and a number (2). Any arithmetic operation involving NaN will result in NaN.
• Therefore, the output of the code console.log("A" - "B" + 2); would be NaN.

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Question 1

Answer 2

• This code block creates a for loop that iterates over i from 0 to 4. For each iteration of the loop, it schedules a function call to console.log(i) using the setTimeout method with a delay of 100 milliseconds.
• The setTimeout method is used to execute a function after a specified delay. In this case, the function is an arrow function that logs the value of i to the console.
• However, because of the asynchronous nature of the setTimeout method, the function calls are not executed immediately, and the loop continues to run before the scheduled function calls are executed.
• When the scheduled function calls are eventually executed, they will use the value of i that exists at the time of execution. At this point, the for loop has already completed and the value of i is equal to 5.
• As a result, the output of this code block will be five 5 logged to the console with a delay of 100 milliseconds between each log statement.

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Question 2

Answer 3

• This code block creates three objects: a, b, and c. a has a property b with a value of 1, and b has a property c with a value of 2.
• The "..." operator is the spread operator, which is used to expand the properties of an object into another object or an array. In this code block, the spread operator is used to create a new object c that combines the properties of a and b.
• The spread operator in const c = {...a, ...b}; first spreads the properties of a into c, and then spreads the properties of b into c. Since there are no common property names between a and b, the properties are simply added to c.
• Therefore, the value of c will be an object with two properties: b with a value of 1 and c with a value of 2.
• The output of console.log(c); will be {b: 1, c: 2}.

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Question 3

Answer 4

• In JavaScript, when using the equality operator (==) to compare two values, if the operands are of different types, JavaScript tries to convert one or both of the operands to a common type before making the comparison.
• In this code block, a and b are both arrays containing the same values [1, 2, 3]. c is a string that contains the same values as a and b, separated by commas.
• When a == c is evaluated, JavaScript tries to convert c to an array. Since c is a string, it is converted to an array with one element, which is the string "1,2,3". This is not equal to a, which is an array with three elements, so the expression evaluates to false.
• Similarly, when b == c is evaluated, JavaScript tries to convert c to an array. Again, c is converted to an array with one element, which is the string "1,2,3". This is not equal to b, which is an array with three elements, so the expression evaluates to false.
• However, when a == b is evaluated, both operands are arrays of the same type, so JavaScript compares the values of the arrays. Even though a and b contain the same values, they are different arrays in memory, so the expression evaluates to false.
• Therefore, the output of console.log(a == c); and console.log(b == c); will be false, and the output of console.log(a == b); will also be false.

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Question 4

Answer 5

• In this code block, a is a function that returns the arguments object. The arguments object is a built-in object in JavaScript that is available inside functions and contains an array-like list of the arguments passed to the function.
• When a is called with the arguments 1, 2, and 3 (a(1, 2, 3)), it returns the arguments object that contains an array-like list of the arguments passed to the function. In this case, the arguments object will contain three elements: 1, 2, and 3.
• The output of console.log(a(1, 2, 3)); will be the arguments object, which looks like an array but is not an actual array. Depending on the environment, the output may look something like this: Arguments [ 1, 2, 3 ] Or Arguments { '0': 1, '1': 2, '2': 3 }
• In general, it's not recommended to use the arguments object in modern JavaScript code because it can make code harder to read and maintain. Instead, it's better to use the rest parameter syntax (...args) to capture a variable number of arguments as an actual array.

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Question 5

Answer 6

• In this code block, a is an array with three elements [1, 2, 3]. However, when a[10] = 10 is executed, a new element is added to the array at index 10, with the value 10. This means that the array a now has a length of 11, and the elements at indices 3 through 9 are undefined.
• When console.log(a) is called, the output will be the array a, which looks something like this: [1, 2, 3, undefined, undefined, undefined, undefined, undefined, undefined, undefined, 10]
• When console.log(a.length) is called, the output will be the length of the array a, which is 11. Even though only four elements have been explicitly defined in the array (a[0], a[1], a[2], and a[10]), JavaScript automatically assigns a length to the array based on the highest index that has been assigned a value plus one. In this case, the highest index assigned a value is 10, so the length of the array is 11.

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Question 6

Answer 7

• In this code block, a is an array with three elements [1, 2, 3]. However, when a[-1] = 0 is executed, a new element is added to the array at index -1, with the value 0. This might seem unusual, but in JavaScript, array indices are actually just object property names, and any property name can be used, including negative numbers. However, using negative indices can make code harder to read and understand, so it's generally not recommended.
• When console.log(a) is called, the output will be the array a, which looks something like this: [1, 2, 3, '-1': 0]
• Notice that the element at index -1 is included in the output as a property with the name '-1'.
• When console.log(a.length) is called, the output will be the length of the array a, which is 3. This is because the length property of an array in JavaScript always returns one more than the highest index in the array. In this case, the highest index is 2, so the length of the array is 3. The fact that there is a property with the name '-1' does not affect the length of the array, since the length property only considers elements with non-negative integer indices.

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Question 7

Answer 8

• In this code block, a and b are two objects with properties a, b, c and b, c, 4 respectively. When c is assigned the result of the spread operation {...a, ...b}, it creates a new object c by combining the properties of a and b using the spread operator.
• The resulting object c will have the properties of both a and b, and any properties with the same name will be overwritten by the value of the property from b. In this case, since both a and b have a property named b, the value of b in the resulting object c will be 3 (from b). Similarly, c will have properties a, b, and c, with values 1, 3, and 4, respectively.
• When console.log(c) is called, the output will be the object c, which looks something like this: {a: 1, b: 3, c: 4}
• Notice that the b property in c has the value 3, which was taken from b and overwritten the value of b in a.

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Question 8

Answer 9

• The NaN (Not a Number) value in JavaScript is a special value that represents the result of an undefined or unrepresentable mathematical operation, such as dividing zero by zero, or multiplying infinity by zero. NaN is a numeric value, but it is not equal to any other value, including itself.
• When console.log(typeof NaN) is called, the output will be number. This is because NaN is considered a special numeric value in JavaScript.
• When console.log(NaN == NaN) is called, the output will be false. This is because NaN is not equal to any value, including itself. Even though NaN is a numeric value, it is not considered equal to any other numeric value or NaN itself.
• When console.log(NaN === NaN) is called, the output will also be false. This is because the === operator tests for both equality of value and type, and since both NaN values are of the same type (number), the result is still false.
• Therefore, it is important to be careful when working with NaN in JavaScript and to check for NaN values explicitly, such as by using the isNaN() function or the Number.isNaN() method.

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Question 9

Answer 10

• In this code block, a is a constant string variable containing the value "hello". When the toUpperCase() method is called on a, it returns a new string with all characters in uppercase, but it does not modify the original string a itself.
• Therefore, even though the toUpperCase() method is called on a, the value of a itself remains unchanged and still contains the string "hello". When console.log(a) is called, the output will be "hello", since the value of a has not been modified by the previous call to toUpperCase().
• If you want to change the value of a to the uppercase version of "hello", you need to assign the result of the toUpperCase() method back to a, like this:
• const a = "hello";
• a = a.toUpperCase();
• console.log(a); // "HELLO"
• In this case, the value of a will be "HELLO", since it has been assigned the result of calling toUpperCase() on the original string "hello".

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Question 10

How many did you got right✅? Let me know in the comments 🤖