Encapsulating Data with Private Class Fields

Snippet

Encapsulating Data with Private Class Fields

Private class fields (marked with #) ensure that sensitive data or internal helper methods cannot be accessed or modified from outside the class instance.

snippet.js
javascript
class ApiService {
  #apiKey;
 
  constructor(key) {
    this.#apiKey = key;
  }
 
  #buildHeaders() {
    return { 'Authorization': `Bearer ${this.#apiKey}` };
  }
 
  async fetchData(url) {
    const headers = this.#buildHeaders();
    return fetch(url, { headers });
  }
}

nodejs

Breakdown

#apiKey;

Declares a private field that is not accessible via instance property lookup.

#buildHeaders()

Defines a private method that can only be called from within other methods of the same class.

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Encapsulating Data with Private Class Fields

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