paioleiro/simple-calculator

simple-calculator is a small web based calculator built with plain HTML, CSS, and JavaScript, with no extra frameworks or libraries involved. It supports the four basic arithmetic operations of addition, subtraction, multiplication, and division, plus decimal number input, a clear button, and a delete or backspace style key for correcting a mistake. It also has a responsive layout, meaning it should adjust reasonably well to different screen sizes, and it works both with mouse clicks on the on-screen buttons and with keyboard input. The project is organized into three simple files: one HTML file for the page structure and layout of the buttons and display, one CSS file for the visual styling, and one JavaScript file that contains the actual calculator logic along with the code that listens for keyboard presses. Typing numbers, a period for decimals, the operator symbols for plus, minus, multiply, and divide, pressing Enter to get the result, Backspace to delete the last entry, and Escape to clear everything, all work the same as clicking the equivalent on-screen buttons. To try it out, you simply open the index.html file directly in a web browser, either by double clicking it or by serving it with a small local development server such as live-server. There is no build step, installation process, or external dependency required. The README also lists a few optional next steps the author has not yet done, such as adding automated tests, animations, a calculation history, or more advanced scientific functions. The project is released under the MIT license, and the author explicitly says it is fine to reuse and modify.