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Project Design Document: Day.js

BUSINESS POSTURE

Day.js is a minimalist JavaScript library that parses, validates, manipulates, and displays dates and times for modern browsers with a largely Moment.js-compatible API. It's designed to be a lightweight alternative to Moment.js, addressing the issue of Moment.js's large size.

Priorities:

  • Minimize library size to reduce impact on application load times and bandwidth consumption.
  • Maintain high API compatibility with Moment.js to ease migration for existing users.
  • Ensure cross-browser compatibility and consistent behavior.
  • Provide a simple, easy-to-use API for date and time manipulation.
  • Provide high test coverage.

Goals:

  • Provide a smaller, faster alternative to Moment.js.
  • Facilitate easy date and time operations in web applications.
  • Reduce the overhead associated with date/time libraries in web projects.

Business Risks:

  • Incompatibility: Subtle differences in behavior compared to Moment.js could break existing applications that rely on precise Moment.js behavior.
  • Maintainability: As a community-maintained project, long-term maintenance and updates depend on community contributions. Lack of active maintenance could lead to security vulnerabilities or incompatibility with future browser updates.
  • Bugs and Security Vulnerabilities: Despite efforts to maintain a small codebase, undiscovered bugs or vulnerabilities could impact applications using the library, potentially leading to incorrect date/time calculations or other issues.

SECURITY POSTURE

Existing Security Controls:

  • security control: Extensive Test Suite: The project includes a comprehensive test suite to ensure functionality and prevent regressions. Location: /test directory in the GitHub repository.
  • security control: Static Code Analysis: The project uses linters (like ESLint) to enforce code style and identify potential issues. Location: .eslintrc.js configuration file and package.json scripts in the GitHub repository.
  • security control: Dependency Management: The project has very few external dependencies, reducing the risk of supply chain attacks. Location: package.json file in the GitHub repository.
  • security control: Immutable Design: Day.js objects are immutable after creation, preventing unintended side effects from date manipulations. Location: This is a design principle described in the documentation and enforced through the library's implementation.

Accepted Risks:

  • accepted risk: Limited Time Zone Handling: While Day.js supports IANA time zones through plugins, complex time zone calculations might have edge cases or performance considerations.
  • accepted risk: Reliance on Browser APIs: The library relies on the browser's built-in Date object and related APIs, which may have slight variations or inconsistencies across different browsers and versions.
  • accepted risk: Community-Driven Security Updates: Vulnerability patching relies on community contributions and reporting, which may introduce delays in addressing newly discovered security issues.

Recommended Security Controls:

  • security control: Regular Dependency Audits: Implement automated dependency scanning to identify and address vulnerabilities in any (even indirect) dependencies.
  • security control: Content Security Policy (CSP) Compatibility: Ensure the library is compatible with strict CSP configurations to mitigate the risk of XSS attacks in applications using Day.js.
  • security control: Security-Focused Code Reviews: Emphasize security considerations during code reviews, particularly for changes related to parsing, formatting, and time zone handling.

Security Requirements:

  • Authentication: Not applicable, as Day.js is a client-side library and does not handle authentication.
  • Authorization: Not applicable, as Day.js is a client-side library and does not handle authorization.
  • Input Validation:
    • Requirement: The library should gracefully handle invalid date/time inputs, returning predictable results (e.g., an "Invalid Date" object) rather than throwing errors or causing unexpected behavior.
    • Requirement: The library should provide clear mechanisms for validating user-provided date/time strings before parsing.
  • Cryptography: Not directly applicable, as Day.js does not perform cryptographic operations. However, if used in contexts where dates/times are part of security-sensitive data, ensure that appropriate cryptographic measures are applied externally.
  • Output Encoding: Not applicable.

DESIGN

C4 CONTEXT

graph LR
    User["User/Web Browser"] -- Uses --> DayJS["Day.js Library"]
    DayJS -- Uses --> IntlAPI["Browser Intl API"]
    DayJS -- Uses --> DateAPI["Browser Date API"]
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Element Description:

  • Element:

    • Name: User/Web Browser
    • Type: User
    • Description: The end-user interacting with a web application that utilizes Day.js.
    • Responsibilities: Interacts with the web application, triggering date and time operations.
    • Security controls: Browser security features (e.g., same-origin policy, CSP).

  • Element:

    • Name: Day.js Library
    • Type: Software System
    • Description: The Day.js library itself, embedded within a web application.
    • Responsibilities: Provides date and time parsing, manipulation, validation, and formatting functionalities.
    • Security controls: Immutable objects, input validation, extensive test suite.

  • Element:

    • Name: Intl API
    • Type: External Dependency
    • Description: The browser's built-in Internationalization API, used for locale-aware formatting.
    • Responsibilities: Provides locale-specific date and time formatting capabilities.
    • Security controls: Relies on browser's implementation, assumed to be secure.

  • Element:

    • Name: Date API
    • Type: External Dependency
    • Description: The browser build-in Date API.
    • Responsibilities: Provides date and time objects.
    • Security controls: Relies on browser's implementation, assumed to be secure.

C4 CONTAINER

graph LR
    User["User/Web Browser"] -- Uses --> WebApp["Web Application"]
    WebApp -- Uses --> DayJSAPI["Day.js API"]
    DayJSAPI -- Uses --> Plugins["Plugins (optional)"]
    DayJSAPI -- Uses --> Core["Core Functionality"]
    Core -- Uses --> IntlAPI["Browser Intl API"]
    Core -- Uses --> DateAPI["Browser Date API"]
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Element Description:

  • Element:

    • Name: User/Web Browser
    • Type: User
    • Description: The end-user interacting with the web application.
    • Responsibilities: Interacts with the web application, triggering date and time operations.
    • Security controls: Browser security features (e.g., same-origin policy, CSP).

  • Element:

    • Name: Web Application
    • Type: Container
    • Description: The web application that integrates Day.js.
    • Responsibilities: Uses Day.js for date and time related operations within its logic.
    • Security controls: Application-specific security controls (e.g., input validation, output encoding, authentication, authorization).

  • Element:

    • Name: Day.js API
    • Type: Container
    • Description: The public API exposed by Day.js.
    • Responsibilities: Provides methods for parsing, manipulating, validating, and formatting dates and times.
    • Security controls: Input validation, consistent error handling.

  • Element:

    • Name: Plugins (optional)
    • Type: Container
    • Description: Optional plugins that extend Day.js functionality (e.g., time zone support, advanced formatting).
    • Responsibilities: Provide additional features beyond the core library.
    • Security controls: Plugin-specific security controls, code reviews.

  • Element:

    • Name: Core Functionality
    • Type: Container
    • Description: The core logic of Day.js.
    • Responsibilities: Implements the core date/time operations and interacts with the browser's Date object.
    • Security controls: Immutable objects, internal validation checks.

  • Element:

    • Name: Intl API
    • Type: External Dependency
    • Description: The browser's built-in Internationalization API.
    • Responsibilities: Provides locale-specific date and time formatting capabilities.
    • Security controls: Relies on browser's implementation, assumed to be secure.

  • Element:

    • Name: Date API
    • Type: External Dependency
    • Description: The browser build-in Date API.
    • Responsibilities: Provides date and time objects.
    • Security controls: Relies on browser's implementation, assumed to be secure.

DEPLOYMENT

Day.js is a client-side JavaScript library, and therefore, it doesn't have a traditional "deployment" in the sense of server-side applications. Instead, it's distributed and integrated into web applications.

Possible Distribution/Integration Methods:

  1. NPM/Yarn: Installed as a package dependency via npm or yarn and bundled into the application's JavaScript code using a module bundler (e.g., Webpack, Parcel, Rollup).
  2. CDN: Included directly in the HTML using a <script> tag pointing to a CDN (e.g., jsDelivr, unpkg).
  3. Direct Download: Downloaded from the GitHub repository and included as a static asset in the web application.

Chosen Method (for detailed description): NPM/Yarn + Module Bundler

This is the most common and recommended approach for modern web development.

graph LR
    DevMachine["Developer Machine"] -- "npm install dayjs" --> NodeModules["node_modules"]
    NodeModules -- "Bundling (Webpack/Parcel/etc.)" --> BundledJS["Bundled JavaScript File(s)"]
    BundledJS -- "Deployment (e.g., to CDN, Web Server)" --> WebServer["Web Server/CDN"]
    WebServer -- "HTTP Request" --> UserBrowser["User's Browser"]
    UserBrowser -- "Executes JavaScript" --> DayJSExecution["Day.js Execution"]
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Element Description:

  • Element:

    • Name: Developer Machine
    • Type: Environment
    • Description: The developer's local development environment.
    • Responsibilities: Writing code, managing dependencies, building the application.
    • Security controls: Local development environment security best practices.

  • Element:

    • Name: node_modules
    • Type: Directory
    • Description: Local directory where npm/yarn install project dependencies.
    • Responsibilities: Contains all project dependencies, including Day.js.
    • Security controls: Dependency management tools, vulnerability scanning.

  • Element:

    • Name: Bundled JavaScript File(s)
    • Type: Artifact
    • Description: The output of the module bundler, containing the application code and Day.js.
    • Responsibilities: Delivered to the user's browser to execute the application.
    • Security controls: Minification, obfuscation (optional), integrity checks (Subresource Integrity - SRI).

  • Element:

    • Name: Web Server/CDN
    • Type: Infrastructure
    • Description: The server or CDN that hosts the bundled JavaScript file(s).
    • Responsibilities: Serves the application files to the user's browser.
    • Security controls: HTTPS, appropriate caching headers, WAF (Web Application Firewall).

  • Element:

    • Name: User's Browser
    • Type: Environment
    • Description: The user's web browser.
    • Responsibilities: Downloads and executes the JavaScript code, including Day.js.
    • Security controls: Browser security features (e.g., same-origin policy, CSP).

  • Element:

    • Name: Day.js Execution
    • Type: Process
    • Description: The execution of Day.js code within the browser.
    • Responsibilities: Performing date/time operations as requested by the application.
    • Security controls: Relies on the security of the browser's JavaScript engine and Day.js's internal security measures.

BUILD

Day.js uses a build process to create different distribution files (e.g., minified versions, UMD modules, ES modules) and to run tests.

graph LR
    Developer["Developer"] -- "Writes Code" --> SourceCode["Source Code (src/)"]
    SourceCode -- "npm run build" --> BuildScript["Build Script (rollup.config.js)"]
    BuildScript -- "Transpilation (Babel)" --> TranspiledCode["Transpiled Code"]
    TranspiledCode -- "Minification (Terser)" --> MinifiedCode["Minified Code (dist/)"]
    SourceCode -- "npm test" --> TestScript["Test Script"]
    TestScript -- "Runs Tests (Jest)" --> TestResults["Test Results"]
    MinifiedCode -- "Publish (npm)" --> NPMRegistry["NPM Registry"]
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Security Controls in the Build Process:

  • security control: Linting: ESLint is used to enforce code style and identify potential errors, including some security-related issues.
  • security control: Testing: A comprehensive test suite (using Jest) is run as part of the build process to ensure code correctness and prevent regressions.
  • security control: Dependency Management: package-lock.json or yarn.lock are used to ensure consistent and reproducible builds, reducing the risk of unexpected dependency changes.
  • security control: Build Script: The build process is automated using Rollup, a module bundler, which helps ensure consistency and reduces the risk of manual errors.
  • security control: Transpilation: Babel is used to transpile the code to support older browsers, ensuring wider compatibility and reducing the risk of vulnerabilities in older JavaScript engines.
  • security control: Minification: Terser is used to minify the code, reducing the file size and making it slightly more difficult to reverse engineer (though this is not a primary security measure).

RISK ASSESSMENT

Critical Business Processes:

  • Accurate Date/Time Display: Displaying correct dates and times to users is crucial for many applications, especially those dealing with scheduling, events, financial transactions, or any time-sensitive data.
  • Consistent Date/Time Handling: Ensuring consistent behavior across different browsers and time zones is essential for data integrity and user experience.
  • Efficient Date/Time Operations: Performing date/time calculations efficiently is important for application performance, especially in applications that handle large amounts of date/time data.

Data Sensitivity:

  • Day.js itself does not handle sensitive data directly. It primarily deals with date and time values, which are generally not considered sensitive in isolation.
  • However, the context in which Day.js is used might involve sensitive data. For example:
    • Financial applications: Dates and times of transactions.
    • Healthcare applications: Dates and times of appointments, medical records.
    • Authentication systems: Timestamps for login attempts, password resets.
  • Therefore, while Day.js itself doesn't handle sensitive data, applications using it must implement appropriate security measures to protect any sensitive data that includes date/time information.

QUESTIONS & ASSUMPTIONS

Questions:

  • Are there any specific compliance requirements (e.g., GDPR, HIPAA) that the applications using Day.js need to adhere to? This would influence how date/time data is stored and processed.
  • Are there any specific performance requirements for date/time operations? This might influence the choice of Day.js plugins or the need for custom date/time handling logic.
  • What level of browser support is required? This will determine the necessary transpilation steps in the build process.
  • Are there any plans to add new features or plugins to Day.js? This could impact the security posture and require further analysis.

Assumptions:

  • BUSINESS POSTURE: It is assumed that the primary goal is to provide a lightweight and Moment.js-compatible date/time library.
  • BUSINESS POSTURE: It is assumed that the project is community-maintained and relies on contributions for updates and security patches.
  • SECURITY POSTURE: It is assumed that the browser's built-in Date object and related APIs are reasonably secure and reliable.
  • SECURITY POSTURE: It is assumed that developers using Day.js will implement appropriate security measures in their applications to protect any sensitive data that includes date/time information.
  • DESIGN: It is assumed that the NPM/Yarn + Module Bundler distribution method is the primary way Day.js will be integrated into web applications.
  • DESIGN: It is assumed that developers will use the provided plugins for features like time zone support, rather than implementing custom solutions.