Programmable Calculator

Usage Instructions:

1. Enter Expression: In the “Enter Expression” input field, type the mathematical expression or function you wish to evaluate.
2. Define Custom Functions: In the “Define Custom Functions” textarea, you can write custom JavaScript functions. For example, to define a function that doubles a number, you can write:

3. Once you’ve defined your custom function, you can use it in the expression input. For instance, entering myFunc(5) and pressing “Calculate” will return 10.
4. Click the “Calculate” button to evaluate your expression or function. The result will be displayed below.

Remember, while this example showcases the flexibility of a programmable calculator, it’s essential to ensure user input is validated and sanitized properly to prevent malicious code execution in real-world applications.