https://www.duncanleung.com/blog 📚 Learning, 👨🏻‍💻 Building, 📝 Documenting... en-us duncan@leungs.email (Duncan Leung) duncan@leungs.email (Duncan Leung) Sun, 22 Jun 2025 00:00:00 GMT https://www.duncanleung.com/blog/claude-code-global-mcp-config https://www.duncanleung.com/blog/claude-code-global-mcp-config Learn how to configure MCP (Model Context Protocol) servers globally for Claude Code, making them available across all your projects. Sun, 22 Jun 2025 00:00:00 GMT duncan@leungs.email (Duncan Leung) claude-codemcp https://www.duncanleung.com/blog/eslint-v9-typescript https://www.duncanleung.com/blog/eslint-v9-typescript A guide to the upcoming changes in ESLint v9 regarding TypeScript integration, including migration notes. Thu, 18 Jul 2024 00:00:00 GMT duncan@leungs.email (Duncan Leung) eslinttypescript https://www.duncanleung.com/blog/image-scrolling-loading https://www.duncanleung.com/blog/image-scrolling-loading How to solve one of the most frustrating UX issues in chat applications: ensuring automatic scrolling works correctly when images load asynchronously. Tue, 16 Apr 2024 00:00:00 GMT duncan@leungs.email (Duncan Leung) reactDOM https://www.duncanleung.com/blog/useref-resize-observer-react-dynamic-measurements https://www.duncanleung.com/blog/useref-resize-observer-react-dynamic-measurements Why useRef alone is insufficient for dynamic measurements, and how to combine it with ResizeObserver and useState for responsive UI. Tue, 16 Apr 2024 00:00:00 GMT duncan@leungs.email (Duncan Leung) reactDOM https://www.duncanleung.com/blog/missing-initial-state-firebase-auth-proxy-nextjs-vercel https://www.duncanleung.com/blog/missing-initial-state-firebase-auth-proxy-nextjs-vercel Solving Firebase Auth redirect issues on Vercel by implementing a proxy solution to handle SAML SSO authentication and resolve missing initial state errors. Sat, 23 Sep 2023 00:00:00 GMT duncan@leungs.email (Duncan Leung) firebaseauthentication https://www.duncanleung.com/blog/go-idiom-accept-interfaces-return-types https://www.duncanleung.com/blog/go-idiom-accept-interfaces-return-types Understanding the Go idiom of accepting interfaces and returning concrete types to write flexible, reusable, and maintainable code. Fri, 30 Jun 2023 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/allocating-memory-go https://www.duncanleung.com/blog/allocating-memory-go Understanding memory allocation in Go, including stack vs heap allocation, escape analysis, and how Go handles pointer returns from functions. Wed, 28 Jun 2023 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/methods-in-go https://www.duncanleung.com/blog/methods-in-go Understanding Go methods, the difference between value and pointer receivers, embedding for composition, and how interfaces work with methods. Wed, 28 Jun 2023 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/slices-in-go https://www.duncanleung.com/blog/slices-in-go Understanding Go slices, their underlying array structure, creation and modification mechanics, and the implications when passing slices to functions. Mon, 26 Jun 2023 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/go-json-encoding-and-decoding https://www.duncanleung.com/blog/go-json-encoding-and-decoding A guide to JSON serialization and deserialization in Go, covering type mappings, HTTP responses, and practical examples with the net/http package. Mon, 19 Jun 2023 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/go-function-arguments-passed-by-value https://www.duncanleung.com/blog/go-function-arguments-passed-by-value How Go passes function arguments by value and the implications for different data types: integers, pointers, slices, strings, and structs. Thu, 08 Jun 2023 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/tailwind-css-unknown-at-rule https://www.duncanleung.com/blog/tailwind-css-unknown-at-rule Fixing VSCode warnings for Tailwind CSS directives by creating custom CSS data configuration files for proper syntax recognition. Wed, 11 Jan 2023 00:00:00 GMT duncan@leungs.email (Duncan Leung) tailwindcss https://www.duncanleung.com/blog/nvm-commands-cheatsheet https://www.duncanleung.com/blog/nvm-commands-cheatsheet A comprehensive cheatsheet for Node Version Manager (NVM) commands including installation, version switching, aliasing, and management. Fri, 23 Dec 2022 00:00:00 GMT duncan@leungs.email (Duncan Leung) nodejsnvm https://www.duncanleung.com/blog/understand-go-golang-interfaces https://www.duncanleung.com/blog/understand-go-golang-interfaces A guide to understand Go interfaces through a power socket and electrical device analogy, covering duck typing and interface implementation. Thu, 23 Dec 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/recover-accidental-git-push-force https://www.duncanleung.com/blog/recover-accidental-git-push-force How to recover from an accidental git push --force by using git reflog to find the previous commit and restore the branch to its original state. Thu, 16 Dec 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) git https://www.duncanleung.com/blog/next-js-typescript-svg-any-module-declaration https://www.duncanleung.com/blog/next-js-typescript-svg-any-module-declaration Fixing TypeScript ESLint errors when using SVGs with Next.js 11 by creating custom module declarations and configuring TypeScript properly. Sat, 10 Jul 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) typescriptnextjs https://www.duncanleung.com/blog/go-basic-data-structures-types-pointers-structs-arrays-slices-int-float-string https://www.duncanleung.com/blog/go-basic-data-structures-types-pointers-structs-arrays-slices-int-float-string Understanding Go data structures and their memory layout including integers, floats, arrays, pointers, structs, strings, and slices. Fri, 09 Jul 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/find-kill-process-port-3000-mac https://www.duncanleung.com/blog/find-kill-process-port-3000-mac How to find and kill processes running on specific ports like 3000 on macOS using lsof and kill commands. Wed, 30 Jun 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) macos https://www.duncanleung.com/blog/iterating-index-strings-runes-go-golang https://www.duncanleung.com/blog/iterating-index-strings-runes-go-golang Understanding the difference between indexing strings as bytes versus runes in Go, and when to use each approach for proper Unicode handling. Wed, 16 Jun 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/husky-prettier-eslint-precise-commits-lint-staged-pre-commit-pre-push https://www.duncanleung.com/blog/husky-prettier-eslint-precise-commits-lint-staged-pre-commit-pre-push Automatically format and lint code with Git hooks using Husky, Prettier, ESLint, precise-commits and lint-staged for pre-commit and pre-push workflows. Sat, 12 Jun 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) eslintprettier https://www.duncanleung.com/blog/golang-readers-writers https://www.duncanleung.com/blog/golang-readers-writers Understanding the io.Reader and io.Writer interfaces in Go, and how accepting an io.Writer parameter makes your code flexible across files, HTTP responses, stdout, and in-memory buffers. Mon, 03 May 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) backendgo https://www.duncanleung.com/blog/eslint-mixed-javascript-typescript-files-codebase https://www.duncanleung.com/blog/eslint-mixed-javascript-typescript-files-codebase Setting up ESLint to parse and lint a mixed JavaScript and TypeScript codebase using overrides configuration for different file types. Wed, 06 Jan 2021 00:00:00 GMT duncan@leungs.email (Duncan Leung) eslinttypescript https://www.duncanleung.com/blog/accessing-material-ui-theme-object-emotion-styled-component-css-prop https://www.duncanleung.com/blog/accessing-material-ui-theme-object-emotion-styled-component-css-prop A guide to access and utilize Material-UI theme objects within Emotion styled components and CSS props, with practical implementation examples. Thu, 22 Oct 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) reactmaterial-uiemotion https://www.duncanleung.com/blog/aws-set-up-email-billing-alert https://www.duncanleung.com/blog/aws-set-up-email-billing-alert A detailed guide to setting up automated email billing alerts in AWS using CloudWatch metrics and SNS notifications for cost monitoring. Wed, 17 Jun 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) awscloudwatchmonitoring https://www.duncanleung.com/blog/serverless-securing-authenticate-aws-api-gateway-endpoints-cognito-iam-api-key https://www.duncanleung.com/blog/serverless-securing-authenticate-aws-api-gateway-endpoints-cognito-iam-api-key A guide to implement authentication and authorization in AWS API Gateway, covering Cognito User Pools, IAM roles, and API keys with practical examples. Sat, 30 May 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) awsserverlesssecurity https://www.duncanleung.com/blog/serverless-set-breakpoint-locally-debug-aws-lambda https://www.duncanleung.com/blog/serverless-set-breakpoint-locally-debug-aws-lambda A step-by-step guide to setting up and using breakpoints for local debugging of AWS Lambda functions, improving serverless development workflow. Thu, 28 May 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) awsserverlessdebugging https://www.duncanleung.com/blog/serverless-pseudo-parameters-reference-another-lambda https://www.duncanleung.com/blog/serverless-pseudo-parameters-reference-another-lambda A detailed guide to using Serverless Framework pseudo parameters for referencing Lambda functions and other AWS resources in your serverless applications. Sun, 10 May 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) awsserverless https://www.duncanleung.com/blog/visual-studio-code-yml-custom-serverless-tag https://www.duncanleung.com/blog/visual-studio-code-yml-custom-serverless-tag Learn how to set up VS Code to properly recognize and validate custom YAML tags used in Serverless Framework configuration files. Fri, 08 May 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) vscodeserverless https://www.duncanleung.com/blog/react-state-rerender-useeffect https://www.duncanleung.com/blog/react-state-rerender-useeffect A mental model for useEffect — moving past the lifecycle (mount/update/unmount) mindset to thinking about effects as a way to synchronize side effects with React state and props. Tue, 05 May 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) reacthooks https://www.duncanleung.com/blog/switch-multiple-aws-profile-aws-cli-serverless https://www.duncanleung.com/blog/switch-multiple-aws-profile-aws-cli-serverless A guide to set up and switch between multiple AWS profiles when working with AWS CLI and Serverless Framework projects. Tue, 05 May 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) awsserverless https://www.duncanleung.com/blog/how-to-teach-programming-the-importance-of-mental-models https://www.duncanleung.com/blog/how-to-teach-programming-the-importance-of-mental-models Exploring effective programming education through mental models, with practical strategies for building conceptual understanding and improving outcomes. Thu, 30 Apr 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) programminglearning https://www.duncanleung.com/blog/select-contentful-locale-gatsby-context-graphql-variable https://www.duncanleung.com/blog/select-contentful-locale-gatsby-context-graphql-variable A detailed guide to implementing dynamic locale selection in Gatsby using Contentful, GraphQL variables, and React Context for internationalized content. Mon, 27 Apr 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) graphqlgatsbyi18n https://www.duncanleung.com/blog/typescript-type-guards https://www.duncanleung.com/blog/typescript-type-guards A guide to use TypeScript type guards for runtime type checking and type narrowing in your TypeScript applications. Fri, 17 Apr 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) typescript https://www.duncanleung.com/blog/typescript-array-map-over-union-array-type https://www.duncanleung.com/blog/typescript-array-map-over-union-array-type A guide to properly handling array map operations with union types in TypeScript, including type inference and type safety considerations. Thu, 16 Apr 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) typescript https://www.duncanleung.com/blog/python-environment-variables https://www.duncanleung.com/blog/python-environment-variables A guide to manage Python environment variables using dotenv, including best practices for configuration and security. Mon, 06 Apr 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) python https://www.duncanleung.com/blog/testing-react-helmet-document-head-meta-tag-react-testing-library https://www.duncanleung.com/blog/testing-react-helmet-document-head-meta-tag-react-testing-library A detailed guide to testing React Helmet document head meta tags using React Testing Library, including setup, best practices, and common testing patterns. Tue, 18 Feb 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) testingjestreact-testing-library https://www.duncanleung.com/blog/typescript-generics-conditional-types-emotion-as-prop https://www.duncanleung.com/blog/typescript-generics-conditional-types-emotion-as-prop A guide to implement TypeScript generics and conditional types for type-safe Emotion components with dynamic as props, including practical patterns and examples. Mon, 17 Feb 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) typescriptemotion https://www.duncanleung.com/blog/why-slow-plugin-typescript-eslint-performance-issues https://www.duncanleung.com/blog/why-slow-plugin-typescript-eslint-performance-issues A deep dive into TypeScript ESLint plugin performance issues, exploring common bottlenecks and providing solutions for improved linting speed. Mon, 10 Feb 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) eslinttypescript https://www.duncanleung.com/blog/how-to-setup-eslint-eslintrc-config-difference-eslint-config-plugin https://www.duncanleung.com/blog/how-to-setup-eslint-eslintrc-config-difference-eslint-config-plugin A guide to set up ESLint, explaining the differences between ESLint config files and plugins, with detailed configuration examples and best practices. Tue, 28 Jan 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) eslint https://www.duncanleung.com/blog/profile-measure-find-remove-slow-eslint-rules https://www.duncanleung.com/blog/profile-measure-find-remove-slow-eslint-rules A detailed guide to profiling, measuring, and optimizing slow ESLint rules, with practical techniques for improving linting performance. Thu, 16 Jan 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) eslintoptimization https://www.duncanleung.com/blog/typescript-module-declaration-svg-img-assets https://www.duncanleung.com/blog/typescript-module-declaration-svg-img-assets A guide to create TypeScript module declarations for SVG and image assets, including webpack configuration and type definitions. Wed, 15 Jan 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) typescriptwebpack https://www.duncanleung.com/blog/aws-amplify-aws-exports-js-typescript https://www.duncanleung.com/blog/aws-amplify-aws-exports-js-typescript A guide to properly typing and integrating AWS Amplify configuration files in TypeScript projects, with focus on aws-exports.js setup. Mon, 13 Jan 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) awstypescript https://www.duncanleung.com/blog/storybook-decorators-emotion-theme-provider https://www.duncanleung.com/blog/storybook-decorators-emotion-theme-provider A guide to implementing Emotion Theme Provider decorators in Storybook, including troubleshooting common issues and best practices for theme management. Fri, 10 Jan 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) storybookemotion https://www.duncanleung.com/blog/storybook-decorators-react-intl-provider https://www.duncanleung.com/blog/storybook-decorators-react-intl-provider A guide to configure React-Intl Provider decorators in Storybook for internationalization testing, including setup and best practices. Fri, 10 Jan 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) storybooki18n https://www.duncanleung.com/blog/import-svg-storybook-webpack-loader https://www.duncanleung.com/blog/import-svg-storybook-webpack-loader A detailed guide to setting up Webpack loaders in Storybook for importing and using SVG files as React components. Wed, 08 Jan 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) storybookwebpack https://www.duncanleung.com/blog/emotion-css-prop-jsx-pragma-storybook https://www.duncanleung.com/blog/emotion-css-prop-jsx-pragma-storybook A guide to configure Emotion CSS prop with JSX Pragma in Storybook, including setup, troubleshooting, and best practices. Mon, 06 Jan 2020 00:00:00 GMT duncan@leungs.email (Duncan Leung) emotionstorybook https://www.duncanleung.com/blog/git-sync-remote-upstream-fork https://www.duncanleung.com/blog/git-sync-remote-upstream-fork A step-by-step guide to keeping your Git fork in sync with the original upstream repository, including remote tracking and branch management. Wed, 18 Dec 2019 00:00:00 GMT duncan@leungs.email (Duncan Leung) git https://www.duncanleung.com/blog/testing-validation-schema-formik-form https://www.duncanleung.com/blog/testing-validation-schema-formik-form A detailed guide to testing Formik form validation schemas using Jest and React Testing Library, covering validation rules, error handling, and test patterns. Tue, 03 Dec 2019 00:00:00 GMT duncan@leungs.email (Duncan Leung) testingjest https://www.duncanleung.com/blog/python-name-main-pattern https://www.duncanleung.com/blog/python-name-main-pattern An in-depth explanation of the __name__ == __main__ pattern in Python, why it exists, and how to use it effectively in your modules. Mon, 02 Dec 2019 00:00:00 GMT duncan@leungs.email (Duncan Leung) python https://www.duncanleung.com/blog/set-up-python-pyenv-virtualenv-poetry https://www.duncanleung.com/blog/set-up-python-pyenv-virtualenv-poetry A guide to set up a modern Python development environment using pyenv for version management and Poetry for dependency management. Wed, 27 Nov 2019 00:00:00 GMT duncan@leungs.email (Duncan Leung) python https://www.duncanleung.com/blog/fixing-netlify-build-fail https://www.duncanleung.com/blog/fixing-netlify-build-fail A practical guide to diagnosing and resolving common Netlify build failures, including deployment issues and continuous integration troubleshooting. Tue, 26 Nov 2019 00:00:00 GMT duncan@leungs.email (Duncan Leung) netlifydevops https://www.duncanleung.com/blog/hacktoberfest-oc-meetup https://www.duncanleung.com/blog/hacktoberfest-oc-meetup Recap of the Hacktoberfest Orange County meetup — open source contributions, community engagement, and collaborative coding experiences. Tue, 16 Oct 2018 00:00:00 GMT duncan@leungs.email (Duncan Leung) hacktoberfestevents https://www.duncanleung.com/blog/testing-formik-form-onsubmit https://www.duncanleung.com/blog/testing-formik-form-onsubmit A detailed guide to testing Formik form submission handlers using Jest and React Testing Library, including async submissions and validation testing. Mon, 15 Oct 2018 00:00:00 GMT duncan@leungs.email (Duncan Leung) testingjest https://www.duncanleung.com/blog/fixing-react-warning-synthetic-events-in-setstate https://www.duncanleung.com/blog/fixing-react-warning-synthetic-events-in-setstate Understand and resolve React synthetic event warnings in setState, with best practices for event handling and state updates. Mon, 14 Aug 2017 00:00:00 GMT duncan@leungs.email (Duncan Leung) react https://www.duncanleung.com/blog/react-pure-render-this-binding-patterns https://www.duncanleung.com/blog/react-pure-render-this-binding-patterns A deep dive into React pure render optimization and method binding patterns, exploring different approaches for improving component performance. Wed, 02 Aug 2017 00:00:00 GMT duncan@leungs.email (Duncan Leung) reactperformance https://www.duncanleung.com/blog/webpack-build-react-production-windows https://www.duncanleung.com/blog/webpack-build-react-production-windows A guide to configuring Webpack for building optimized React production bundles on Windows, including environment-specific settings and common pitfalls. Mon, 31 Jul 2017 00:00:00 GMT duncan@leungs.email (Duncan Leung) reactwebpack https://www.duncanleung.com/blog/avoiding-react-setstate-pitfalls https://www.duncanleung.com/blog/avoiding-react-setstate-pitfalls A guide to avoiding common pitfalls when using setState in React, including asynchronous updates, batching, and state management patterns. Sat, 15 Jul 2017 00:00:00 GMT duncan@leungs.email (Duncan Leung) react