Operator precedence in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code with mixed operators?

Consider the following JavaScript code snippet. What will it print to the console?

Javascript

console.log(3 + 4 * 2 / (1 - 5) ** 2);

A SyntaxError

B 1

C 3.5

D 3.75

💡 Hint

Remember that exponentiation (**) has higher precedence than multiplication and division, which have higher precedence than addition.

The expression evaluates as 3 + (4 * 2) / ((1 - 5) ** 2) = 3 + 8 / 16 = 3 + 0.5 = 3.5.

❓ Predict Output

intermediate

What is the output of this logical and arithmetic expression?

What will the following code output?

Javascript

console.log(true || false && false);

A true

B false

C SyntaxError

D undefined

💡 Hint

Remember that && has higher precedence than ||.

&& is evaluated first: false && false is false, then true || false is true.

❓ Predict Output

advanced

What is the output of this tricky assignment expression?

What will this code print?

Javascript

let a = 1; let b = 2; let c = 3; console.log(a += b *= c);

A 7

B 6

C 9

D TypeError

💡 Hint

Assignment operators are right-associative and have lower precedence than multiplication.

b *= c means b = b * c = 2 * 3 = 6; then a += b means a = a + b = 1 + 6 = 7; console.log prints 7.

❓ Predict Output

advanced

What is the output of this expression with unary and binary operators?

What will the following code output?

Javascript

console.log(-3 ** 2);

A -6

B 9

C SyntaxError

D -9

💡 Hint

Unary minus has lower precedence than exponentiation in JavaScript, so -3 ** 2 is parsed as -(3 ** 2) = -9.

In JavaScript, unary minus has lower precedence than exponentiation, so -3 ** 2 is parsed as -(3 ** 2) = -9.

❓ Predict Output

expert

What is the output of this complex expression mixing bitwise and logical operators?

What will this code print?

Javascript

console.log((5 & 3) || (0 && 2));

A 0

B 1

C 2

D SyntaxError

💡 Hint

Bitwise AND (&) has higher precedence than logical AND (&&) and logical OR (||).

5 & 3 = 1 (bitwise AND), 0 && 2 = 0 (logical AND), then 1 || 0 = 1 (logical OR).

Practice

1. Which operator has the highest precedence in the expression 3 + 4 * 2?

easy

A. Multiplication (*)

B. Addition (+)

C. Subtraction (-)

D. Division (/)

Solution

1. Step 1: Recall operator precedence rules

   Multiplication and division have higher precedence than addition and subtraction.

2. Step 2: Identify operators in the expression

   The expression has addition (+) and multiplication (*). Multiplication runs first.

3. Final Answer:

   Multiplication (*) -> Option A

4. Quick Check:

   Multiplication > Addition [OK]

Hint: Multiplication/division run before addition/subtraction [OK]

Common Mistakes:

• Thinking addition runs before multiplication
• Ignoring operator precedence
• Assuming left-to-right always applies

2. Which of the following expressions is syntactically correct in JavaScript?

easy

A. 5 + (3 * 2)

B. 5 + * 3

C. 5 + 3 * )2(

D. 5 + 3 * 2)

Solution

1. Step 1: Check each expression for syntax errors

   5 + * 3 has two operators in a row (+ *), which is invalid. 5 + 3 * )2( has misplaced parentheses. 5 + 3 * 2) has an unmatched closing parenthesis.

2. Step 2: Confirm correct syntax

   5 + (3 * 2) uses parentheses correctly and has valid operators and operands.

3. Final Answer:

   5 + (3 * 2) -> Option A

4. Quick Check:

   Valid parentheses and operators [OK]

Hint: Check parentheses and operator placement carefully [OK]

Common Mistakes:

• Misplacing parentheses
• Using two operators together
• Unmatched parentheses

3. What is the output of the following code?

console.log(10 - 2 * 3 + 4 / 2);

medium

A. 8

B. 12

C. 6

D. 10

Solution

1. Step 1: Apply operator precedence

   Multiplication (*) and division (/) run before addition (+) and subtraction (-). Calculate 2 * 3 = 6 and 4 / 2 = 2 first.

2. Step 2: Calculate remaining expression

   Expression becomes 10 - 6 + 2. Calculate left to right: 10 - 6 = 4, then 4 + 2 = 6.

3. Final Answer:

   6 -> Option C

4. Quick Check:

   10 - 6 + 2 = 6 [OK]

Hint: Do * and / before + and -, then left to right [OK]

Common Mistakes:

• Adding before multiplying
• Ignoring division precedence
• Calculating right to left

4. Find the error in this expression:

let result = 5 + 3 * / 2;

medium

A. No error, expression is valid

B. Incorrect use of parentheses

C. Division operator should be replaced with subtraction

D. Missing operand between * and /

Solution

1. Step 1: Analyze the operator sequence

   The expression has '* /' operators together without a number between them, which is invalid syntax.

2. Step 2: Identify the syntax error

   Every operator needs operands on both sides. Here, the '*' operator is missing its right operand before the '/' operator.

3. Final Answer:

   Missing operand between * and / -> Option D

4. Quick Check:

   Operators need operands on both sides [OK]

Hint: Operators must have numbers on both sides [OK]

Common Mistakes:

• Ignoring missing operand
• Assuming expression is valid
• Confusing operator roles

5. Given the expression let x = 4 + 3 * 2 ** 2 / (1 + 1);, what is the value of x?

hard

A. 13

B. 10

C. 11

D. 14

Solution

1. Step 1: Evaluate parentheses and exponentiation first

   Parentheses: (1 + 1) = 2. Exponentiation: 2 ** 2 = 4.

2. Step 2: Calculate multiplication and division left to right

   Expression becomes 4 + 3 * 4 / 2. Calculate 3 * 4 = 12, then 12 / 2 = 6.

3. Step 3: Perform addition

   Finally, 4 + 6 = 10.

4. Final Answer:

   10 -> Option B

5. Quick Check:

   Parentheses & exponentiation first, then * /, then + [OK]

Hint: Do parentheses, then **, then * /, then + [OK]

Common Mistakes:

• Ignoring exponentiation precedence
• Doing addition before multiplication
• Miscomputing parentheses