This is a simple calculator app built using JavaScript that can perform basic arithmetic calculations such as addition, subtraction, multiplication and division.

• Launch the app by opening the index.html file in a web browser.
• Use the number buttons to input the values you want to calculate.
• Use the sign buttons to select the operation you want to perform.
• Click the equals button to get the result of your calculation.
• Click the clear button to reset the calculator.

The calculator app is built using JavaScript and DOM manipulation. Here is a brief explanation of the code:

• The code starts by selecting the necessary HTML elements using document.querySelectorAll() and document.querySelector().
• It then initializes some variables to keep track of the values being entered and the sign of the operation being performed.
• A for loop is used to add event listeners to the number buttons, so that when clicked, the corresponding value is added to the appropriate variable.
• There are separate functions to handle the first value, second value, and sign inputs.
• The equals button has an event listener that calculates the result based on the selected operation and displays it in the result field.
• There are two additional buttons - percent and negative - that modify the values and the result in specific ways.
• Finally, the clear button resets all the values and the result to their original states.

• The calculator could be improved to handle more complex operations, such as parentheses and exponents.
• The code could be refactored to make it more efficient and easier to read.
• Styling could be added to make the calculator more attractive and user-friendly.