If statement in Javascript - Time & Space Complexity

Time Complexity: If statement

O(1)

Understanding Time Complexity

We want to see how the time it takes to run an if statement changes as the input changes.

Does the if statement make the program slower when input grows?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

function checkNumber(num) {
  if (num > 10) {
    return "Greater";
  } else {
    return "Smaller or equal";
  }
}
    

This code checks if a number is greater than 10 and returns a message.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: A single if check (comparison).
• How many times: Exactly once per function call.

How Execution Grows With Input

The if statement runs once no matter what the input number is.

Input Size (n)	Approx. Operations
10	1
100	1
1000	1

Pattern observation: The number of operations stays the same even if the input number changes.

Final Time Complexity

Time Complexity: O(1)

This means the if statement takes the same amount of time no matter how big or small the input is.

Common Mistake

[X] Wrong: "If statements take longer when the input number is bigger."

[OK] Correct: The if check is just one comparison and does not repeat or grow with input size.

Interview Connect

Understanding that simple if statements run in constant time helps you explain how your code behaves clearly and confidently.

Self-Check

"What if we added a loop inside the if statement? How would the time complexity change?"