Enhancing Encapsulation in JavaScript and TypeScript: Are Private Fields the Future?

In recent years, JavaScript has evolved significantly, introducing new syntax and conventions to support better encapsulation and data hiding within classes. One notable addition is the use of the # syntax to declare private fields, offering a truly private scope that cannot be accessed outside the class. Meanwhile, TypeScript continues to provide the private keyword, which enforces access restrictions during development but does not impact the emitted JavaScript code.

The Rise of the # Private Fields in JavaScript

The # syntax was introduced as part of the ECMAScript private class fields proposal, aiming to provide a more robust private member mechanism. Unlike conventional naming conventions or TypeScript’s compile-time checks, the # private fields are enforced at the language level, making the data genuinely inaccessible from outside the class.

Example:

“`js
class User {
#password;

constructor(password) {
this.#password = password;
}

verifyPassword(input) {
return input === this.#password;
}
}
“`

This approach ensures strict encapsulation, preventing accidental or intentional external modifications.

Developer Perspectives: Is the # Syntax Visually Appealing?

While the # syntax offers technical advantages, many developers find it visually unappealing or somewhat cumbersome. Its distinctive appearance can sometimes make code less readable, especially for teams not accustomed to it. Nonetheless, advocates argue that it enhances code correctness by making privacy explicit and enforced at the language level.

TypeScript’s private Keyword: Comfort Over Enforcement

TypeScript has long supported the private keyword, which signals intent and provides compile-time checks to restrict access to class members. This feature aligns with many developers’ preferences, especially since it resembles other languages like Java or C++.

Example:

“`ts
class User {
private password: string;

constructor(password: string) {
this.password = password;
}

verifyPassword(input: string): boolean {
return input === this.password;
}
}
“`

However, it is essential to note that TypeScript’s private is solely a compile-time feature. When the code is transpiled into plain JavaScript, these access modifiers are not enforced, meaning that advanced users can still manipulate the class’s internal state via debugging tools or by directly accessing properties if they are not properly encapsulated.

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