Buggy Code Non Existing Variable in JavaScript

Inside the code editor we've tried to define and call a function that takes a number as argument and prints the double of that number to the console.

So when we ran the code, we expected it to print:

but it seems like we made some mistakes because when we run our code we get a ReferenceError instead.

Assignment:

Your task is to fix our code such that no errors will be produced and it will print the desired output.

Understanding the Problem

The core challenge here is to identify why the function is not working as expected and fix the errors. This problem is significant because understanding how to properly define and call functions is fundamental in JavaScript. Common pitfalls include incorrect function names, missing parameters, or syntax errors.

Approach

To solve this problem, we need to carefully examine the code for any mistakes. A naive approach would be to simply look for syntax errors, but a more thorough approach involves checking the function definition and the function call.

Let's consider a naive solution:

function doubleNumber(num) {
  console.log(num * 2);
}

doubleNumber(10);

This code correctly defines a function doubleNumber that takes a number as an argument and prints its double. The function is then called with the argument 10, which should print 20.

Algorithm

Here is a step-by-step breakdown of the algorithm:

Define a function named doubleNumber that takes one parameter num.
Inside the function, use console.log to print the value of num multiplied by 2.
Call the function doubleNumber with the argument 10.

Code Implementation

// Define the function that takes a number and prints its double
function doubleNumber(num) {
  // Print the double of the number to the console
  console.log(num * 2);
}

// Call the function with the argument 10
doubleNumber(10);

In this code:

The function doubleNumber is defined correctly with one parameter num.
The function uses console.log to print num * 2.
The function is called with the argument 10, which prints 20.

Complexity Analysis

The time complexity of this solution is O(1) because the function performs a constant amount of work regardless of the input size. The space complexity is also O(1) as no additional space is used that grows with the input size.

Edge Cases

Potential edge cases include:

Passing a non-numeric value as an argument.
Passing a negative number or zero.

For example:

doubleNumber("a"); // NaN
doubleNumber(-5); // -10
doubleNumber(0); // 0

Testing

To test the solution comprehensively, consider the following test cases:

Simple positive number: doubleNumber(10); // 20
Zero: doubleNumber(0); // 0
Negative number: doubleNumber(-5); // -10
Non-numeric value: doubleNumber("a"); // NaN

Using a testing framework like Jest can help automate these tests.

Thinking and Problem-Solving Tips

When approaching such problems:

Break down the problem into smaller, manageable parts.
Carefully read the problem statement and understand the requirements.
Write pseudocode before jumping into the actual code.
Test your solution with different inputs to ensure it handles all edge cases.

Conclusion

In this blog post, we discussed how to fix a buggy JavaScript function that prints the double of a number. We covered the problem definition, approach, algorithm, code implementation, complexity analysis, edge cases, and testing. Understanding and solving such problems is crucial for developing strong problem-solving skills in programming.

Additional Resources

For further reading and practice, consider the following resources:

Parameters & Arguments: Buggy Code I in JavaScript