JavaScript object immutability: Object.freeze vs. Object.seal

Immutability in JavaScript is crucial for preventing unwanted modifications to objects, especially in scenarios involving application-wide configurations, state objects, or global constants. While the `const` keyword offers assignment immutability for primitive data types, it does not prevent changes to object properties. JavaScript provides built-in methods like `Object.freeze()` and `Object.seal()` to restrict modifications of objects at varying levels. `Object.freeze()` renders an object completely immutable, disallowing any changes to its properties, while `Object.seal()` allows modification of existing properties but prevents the addition or deletion of properties. Both methods are shallow by default, affecting only the top level of objects unless a custom deep-freezing or deep-sealing function is implemented. Although historically there were performance concerns, modern JavaScript engines have optimized these methods. For comprehensive immutability solutions, developers often turn to libraries such as Immer or Immutable.js, which offer more robust and efficient handling of immutable data structures.