XpressCalc - Excel-Like Formula Processing Library

**XpressCalc ** is a lightweight JavaScript library that enables Excel-like calculations in HTML input fields. It supports numeric inputs, arithmetic operations, and real-time validation.

🚀 Features

• ✅ Supports standard arithmetic operations (+, -, *, /, ()).
• ✅ Allows formulas to begin with = like Excel.
• ✅ Live input sanitization to prevent invalid characters.
• ✅ Rounds results to 2 decimal places.
• ✅ Highlights input errors and alerts users.
• ✅ Lightweight and dependency-free.

📦 Installation

Include the script in your HTML file:

<script src="path/to/XpressCalc.js"></script>

Or, install via npm:

npm install XpressCalc 

🚀 Usage

1️⃣ Initialize Inputs

Ensure your inputs are wrapped inside a container with id="calc-zone" and have the attribute data-class="Currency".

<div id="calc-zone">
    <input type="text" data-class="Currency" placeholder="Enter formula or number">
    <input type="text" data-class="Currency" placeholder="Enter another value">
</div>

2️⃣ Automatic Calculation

The library will automatically process the input on focusout:

XpressCalc .attachEventListeners();

3️⃣ Supported Input Formats

Input	Valid?	Result
=10+20	✅ Yes	30
=100/2+5	✅ Yes	55
50	✅ Yes	50
=10*-5	❌ No	Error (Negative values not allowed)
abc123	❌ No	Error

⚡ API Methods

XpressCalc.processSingleInput(input)

Manually process an input field.

const input = document.querySelector('input');
XpressCalc.processSingleInput(input);

XpressCalc.validateKeypress(event)

Prevents invalid characters from being entered.

document.querySelector('input').addEventListener('keydown', XpressCalc.validateKeypress.bind(XpressCalc));

XpressCalc.setError(input, message)

Applies error styling and focus.

XpressCalc.setError(document.querySelector('input'), 'Invalid input!');

XpressCalc.clearError(input)

Removes error styling.

XpressCalc.clearError(document.querySelector('input'));

🛠️ Customization

Modify styles for error highlighting:

input.error {
    border: 2px solid red;
    background-color: #ffe6e6;
}

📜 License

This project is licensed under the MIT License - see the LICENSE file for details.

👨‍💻 Author

Gabriel A. - Built with ❤️

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