Calculator

Remember when you wrote your first "Hello World" program? It felt great to see text appear on the screen. But the real magic of web development happens when you build something interactive—something that responds to the user.

Today, we are tackling one of the classic rites of passage for every aspiring web developer: The Four-Function Calculator.

Why a calculator? Because it is the perfect project to demonstrate how the "holy trinity" of the web works together harmoniously:

1. HTML provides the structure (the buttons and the display screen).

2. CSS makes it look neat and organized.

3. JavaScript provides the "brain" to actually do the math.

By the end of this short post, you will have a fully functional calculator running right in your browser that you coded yourself. Let’s dive in.

The Concept

We aren't reinventing the wheel here. We are going to build a standard calculator that can handle addition, subtraction, multiplication, and division.

To do this, we need a few key ingredients in our code:

• A Display Input: An HTML input field where the numbers appear as you type them, and where the final result is shown.

• A Button Grid: A neat layout of numbers (0-9) and operators (+, -, *, /). We'll use CSS Grid to make this easy.

• The eval() function: This is a built-in JavaScript secret weapon that takes a string of text (like "5 + 5") and magically calculates the answer (10). Note: While eval() can be a security risk in complex, public-facing web apps, it is perfectly safe and efficient for a simple, local project like this.