What is BigInt and how is it different from Number?

BigInt is a built-in JavaScript object (introduced in ES2020) that provides a way to represent whole numbers larger than 2^53 - 1 (the largest number JavaScript can reliably represent with the Number primitive).

Key Differences:

| Feature | Number | BigInt |
|---------|--------|--------|
| Maximum Safe Integer | 2^53 - 1 (9,007,199,254,740,991) | No theoretical limit |
| Syntax | 42 | 42n or BigInt(42) |
| Type | "number" | "bigint" |
| Decimals | Supports decimals | Integer only |
| Math Operations | Works with Math object | Cannot use Math object |
| JSON | Native JSON support | No native JSON support |
| Mixing Operations | N/A | Cannot mix with Number without explicit conversion |

Creating BigInt:

     // Using 'n' suffix
     const bigInt1 = 9007199254740991n;
     const bigInt2 = 123456789012345678901234567890n;

     // Using BigInt() function
     const bigInt3 = BigInt("9007199254740991");
     const bigInt4 = BigInt(9007199254740991);

     console.log(typeof bigInt1); // "bigint"
     

Common Use Cases:

     // 1. Large integer arithmetic
     const largeNumber = 9007199254740992n;
     const result = largeNumber + 1n; // 9007199254740993n

     // Problem with Number:
     console.log(9007199254740992 + 1); // 9007199254740992 (incorrect!)
     console.log(9007199254740992n + 1n); // 9007199254740993n (correct!)

     // 2. High-precision calculations
     const factorial = (n) => {
       if (n === 0n) return 1n;
       return n * factorial(n - 1n);
     };
     console.log(factorial(50n)); // Accurate result for 50!

     // 3. Cryptography and unique identifiers
     const uniqueId = 1234567890123456789012345n;

     // Important: Cannot mix BigInt and Number
     const num = 10;
     const big = 20n;
     // console.log(num + big); // TypeError: Cannot mix BigInt and other types
     console.log(BigInt(num) + big); // 30n (correct)
     console.log(num + Number(big)); // 30 (correct, but loses precision for large values)

     // Comparison works across types
     console.log(10n == 10);  // true
     console.log(10n === 10); // false (different types)
     console.log(10n < 15);   // true
     

Limitations:

     // No decimal support
     const decimal = 3.5n; // SyntaxError

     // Cannot use with Math object
     Math.sqrt(16n); // TypeError

     // JSON serialization requires custom handling
     const data = { id: 123n };
     JSON.stringify(data); // TypeError: Do not know how to serialize a BigInt

     // Solution for JSON:
     JSON.stringify(data, (key, value) => 
       typeof value === 'bigint' ? value.toString() : value
     );