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Simple Javascript Calculator Without Eval

Reviewed by Calculator Editorial Team

This simple JavaScript calculator performs basic arithmetic operations without using the eval() function, which is considered a security risk. It's designed to be clean, secure, and easy to understand.

What is a Simple JavaScript Calculator Without Eval?

A simple JavaScript calculator without eval() is a web-based tool that performs basic arithmetic calculations (addition, subtraction, multiplication, and division) using secure JavaScript methods instead of the potentially dangerous eval() function.

The eval() function evaluates JavaScript code represented as a string, which can be a security risk if not properly sanitized. By avoiding eval(), we create a more secure calculator that follows modern JavaScript best practices.

This calculator uses the Function constructor to safely evaluate mathematical expressions, which is considered a safer alternative to eval().

How to Use This Calculator

Using this calculator is straightforward:

  1. Enter your first number in the "First Number" field
  2. Select an operation from the dropdown menu
  3. Enter your second number in the "Second Number" field
  4. Click the "Calculate" button to see the result
  5. Use the "Reset" button to clear all fields

The calculator will display the result in the result panel below the buttons. The chart will show a simple visualization of the calculation.

How This Calculator Works

The calculator uses the following JavaScript code to perform calculations:

function calculate() { const num1 = parseFloat(document.getElementById('num1').value); const num2 = parseFloat(document.getElementById('num2').value); const operation = document.getElementById('operation').value; let result; switch(operation) { case 'add': result = num1 + num2; break; case 'subtract': result = num1 - num2; break; case 'multiply': result = num1 * num2; break; case 'divide': if(num2 === 0) { result = 'Cannot divide by zero'; } else { result = num1 / num2; } break; default: result = 'Invalid operation'; } document.getElementById('result').textContent = result; updateChart(num1, num2, result, operation); }

The calculator first retrieves the values from the input fields and the selected operation. It then uses a switch statement to perform the appropriate calculation. The result is displayed in the result panel and visualized in the chart.

Examples of Calculations

Here are some examples of calculations you can perform with this calculator:

  • 10 + 5 = 15
  • 20 - 7 = 13
  • 4 × 6 = 24
  • 15 ÷ 3 = 5

Try entering these values in the calculator to see how it works in practice.

Frequently Asked Questions

Why is eval() considered dangerous?
eval() can execute arbitrary JavaScript code, which can be a security risk if the input isn't properly sanitized. It can also lead to performance issues and make code harder to debug.
What is the safer alternative to eval()?
The Function constructor or using switch statements with direct operations are considered safer alternatives to eval().
Can this calculator handle negative numbers?
Yes, the calculator can handle negative numbers. Simply enter a negative value in either of the number fields.
What happens if I try to divide by zero?
The calculator will display "Cannot divide by zero" as a result when you attempt to divide by zero.
Is this calculator mobile-friendly?
Yes, the calculator is designed to work well on both desktop and mobile devices.