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JavaScript Numbers

Numbers in JavaScript represent both integers and floating-point values. Unlike many other languages, JavaScript does not differentiate between integer and decimal types. Mastering numbers is essential for calculations, comparisons, and data manipulation.

Key Topics

Integers and Floats

In JavaScript, numbers can be written with or without decimals. Both integers and floating-point values share the same Number type.

let intNum = 42;
let floatNum = 3.14;
console.log("Integer:", intNum);
console.log("Float:", floatNum);

Output

> Integer: 42

> Float: 3.14

Explanation: Both 42 and 3.14 are considered numbers in JavaScript, even though one is an integer and the other a decimal.

Floating-Point Precision

JavaScript uses double-precision floating-point format, which can lead to rounding issues when dealing with very large or very small numbers.

console.log(0.1 + 0.2);

Output

> 0.30000000000000004

Explanation: Due to floating-point precision, 0.1 + 0.2 does not equal exactly 0.3, but a slightly off value.

typeof Number

The typeof operator returns "number" for all numeric values, making it easy to check if a variable holds a numeric value.

let value = 100;
console.log(typeof value);

Output

> number

Explanation: The typeof operator confirms that value is a number.

JavaScript Usage in DOM

This DOM-based example shows how to perform numeric calculations and display the result on a webpage.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Numbers in DOM</title>
</head>
<body>
    <h1>Number Demo</h1>
    <button onclick="calculate()">Calculate</button>
    <p id="result"></p>

    <script>
        function calculate() {
            let a = 10;
            let b = 2;
            let sum = a + b;
            document.getElementById("result").textContent = "Sum: " + sum;
        }
    </script>
</body>
</html>

Key Takeaways

  • Single Number Type: JavaScript uses one type for both integers and floats.
  • Floating-Point Precision: Be aware of rounding errors in calculations.
  • typeof: Use typeof to identify numeric variables.
  • DOM Integration: Perform calculations and update webpage content dynamically.
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