Working with Numbers

JavaScript provides methods for converting and formatting numbers.

These methods help you work with numeric data effectively.

// Converting to Numbers
Number('123');      // 123
parseInt('123');    // 123
parseFloat('123.45'); // 123.45
parseInt('123px');  // 123 (stops at non-digit)

// Checking Numbers
Number.isNaN(NaN);        // true
Number.isFinite(100);     // true
Number.isInteger(100);    // true
Number.isInteger(100.5);  // false

// Formatting Numbers
const num = 123.456789;
num.toFixed(2);        // '123.46' (2 decimals)
num.toPrecision(4);    // '123.5' (4 significant digits)
num.toExponential(2);  // '1.23e+2'

// Number Constants
Number.MAX_VALUE;      // Largest number
Number.MIN_VALUE;      // Smallest positive number
Number.POSITIVE_INFINITY;
Number.NEGATIVE_INFINITY;
Number.NaN;            // Not a Number

// Safe Integers
Number.MAX_SAFE_INTEGER;  // 9007199254740991
Number.MIN_SAFE_INTEGER;  // -9007199254740991
Number.isSafeInteger(100); // true

• Number() - Convert to number
• parseInt() - Parse integer
• parseFloat() - Parse decimal
• toFixed() - Format decimals
• isNaN() - Check if not a number
• isInteger() - Check if integer
• Number constants for limits

<div class="number-demo">
  <h3>Number Formatter</h3>
  <input type="number" id="numInput" value="123.456789" step="any">
  <button onclick="formatNumber()">Format</button>
  <div id="numOutput"></div>
  
  <hr style="margin: 20px 0;">
  
  <h3>Currency Converter</h3>
  <input type="number" id="amount" value="100" min="0">
  <select id="currency">
    <option value="1">USD</option>
    <option value="0.85">EUR (×0.85)</option>
    <option value="0.73">GBP (×0.73)</option>
    <option value="110">JPY (×110)</option>
  </select>
  <button onclick="convertCurrency()">Convert</button>
  <div id="currencyOutput"></div>
</div>