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David Leong

David Leong

Los Angeles, CA, United States
Member since October 23, 2017
David has ten years of experience developing web applications. He primarily uses JavaScript, React.js, Angular, Vue.js, Node.js, HTML, and SCSS for front-end, and works extensively with Rails, Django, and Node.js for back-end programming. David is especially good at producing quality code. He keeps abreast of technology trends always and adopts the best practice in development.
David is now available for hire
Portfolio
  • Volkno (via Toptal)
    React.js, Redux, Highcharts, Node.js, Express.js, Sequelize, MySQL
  • Stitch
    React.js, Redux, Mobx, Angular, Vue.js, Ruby on Rails, Python, Django, Flask
  • CyberCoders
    Ruby on Rails, React.js, Vue.js, AngularJS, Webpack, Node.js, Python, Django...
Experience
  • JavaScript, 8 years
  • Django, 5 years
  • Ruby on Rails (RoR), 5 years
  • Node.js, 5 years
  • Vue.js, 3 years
  • D3.js, 3 years
  • React.js, 3 years
  • Angular, 2 years
Los Angeles, CA, United States
Availability
Part-time
Preferred Environment
Mac OSX, VSCode, Git, SourceTree, Slack
The most amazing...
...thing I've built is the Slack-like text messaging web app using React.js backed by Rails based API.
Employment
  • Senior Full-Stack Web Developer
    Volkno (via Toptal)
    2017 - 2018
    • Worked on as a full-stack developer managing all 3 layers: front-end, back-end and middle-end.
    • Improved interacting with MySQL in Node.js using sequelize ORM.
    • Improved outdated react-boilerplate codebase.
    • Implemented analytics charts using Highcharts.js library.
    • Integrated video player.
    • Increased database performance by adding denormalized fields and adding proper indexes to tables.
    • Added new api endpoints in backend by using best Express.js practice.
    Technologies: React.js, Redux, Highcharts, Node.js, Express.js, Sequelize, MySQL
  • Senior Full-stack Web developer
    Stitch
    2015 - 2017
    • Integrated Redux store management into React.js codebase.
    • Collaborated with back-end developers to optimize and create the best possible user experience.
    • Advocated interaction design best practices with a focus on consistency and usability.
    • Built reusable React.js and Vue.js components.
    • Contributed to three Rails applications.
    • Contributed to three Python projects.
    • Reviewed the pull requests submitted from other front-end developers.
    • Improved live update of the app by using websocket channel events broadcast.
    • Coordinated with the design team to define the data structure.
    • Provided consultation on functionality design and technologies to adopt.
    • Worked on data visualization using D3.js and Highchart.js.
    Technologies: React.js, Redux, Mobx, Angular, Vue.js, Ruby on Rails, Python, Django, Flask
  • Senior Full-stack Web Developer
    CyberCoders
    2012 - 2015
    • Integrated webpack and React.js into Rails framework.
    • Collaborated with User Interface and User Experience team.
    • Integrated and customized material UI into AngularJS project.
    • Ensured the technical feasibility of UI/UX designs.
    • Contributed to two Node.js applications.
    • Took part in making decisions on technologies to use.
    • Integrated Material UI using Vuetify.js into Vue.js project.
    • Contributed to three Rails applications.
    • Contributed to three Django applications.
    • Reviewed the pull requests submitted from other developers.
    • Assured that code quality is above par using code linting tools.
    Technologies: Ruby on Rails, React.js, Vue.js, AngularJS, Webpack, Node.js, Python, Django, Flask
  • Full-stack Web Developer
    Waveguide LLC
    2008 - 2012
    • Served as a full-stack developer using Python, PHP, HTML, CSS and Javascript.
    • Built RESTful APIs using Flask and SqlAlchemy.
    • Created semantic HTML pages.
    • Confirmed that all user input was validated before submitted to back-end.
    • Ensured software compliance with specified standards.
    • Contributed to deployment to hosting server.
    • Implemented page designs in standards-compliant dynamic XHTML and CSS.
    • Maintained reusable components repositories.
    • Researched new support technologies for development goals.
    Technologies: PHP, Python, HTML, CSS, Javascript, Flask, sqlalchemy
Experience
  • Matching Therapeutics to Cancer Patients (Development)

    The MatchTx solution was built to utilize the proprietary algorithms for several different objectives and market segments.

    I was responsible for the doctors facing app, which predicts how well the patient will respond to a drug, or which treatment is best, based on characteristics and outcomes of the best matched cohorts.

    The front-end is built in SPA using React.js.
    The backend provides RESTful APIs to the front-end app and is built with Django-rest-framework.

    In overall, my contributions were:
    - Built the front-end web app using React.js.
    - Implemented graph drawing using highchart.js.
    - Built RESTful APIs using Django rest framework.
    - Implemented the algorithm that predicts biopsy matching the patient using Kaplan Meier estimator.

  • Slack-like Text Messaging Web and Mobile App (Development)

    Text messaging web app for healthcare teams.

    It is a care coordination platform for healthcare teams, where patients and medical staff can interact.

    My contributions were:
    - Integrated Redux store management into React.js codebase.
    - Closely worked with back-end developers to optimize existing Web technology and
    create the best possible user experience.
    - Advocated Web interaction design best practices, with a focus on consistency and
    usability.
    - Built reusable React.js components.
    - Reviewed the pull requests submitted from other front-end developers.
    - Improved live update of the app state by proper handling of websocket channel events
    broadcast.
    - Collaborated with the design team to define the data structure.
    - Provided consultation on functionality design and technologies to adopt.

  • Sell Photography Online (Development)

    This project involved developing online photo storefront.

    Here is how it works:
    1. Setup and upload images
    2. Promote gallery
    3. Sell images
    4. Fulfill orders
    5. Get paid for orders

    As a front-end developer, I built the web app in SPA using Vue.js library.

    My responsibilities were:
    - Build webpack hot-reload config and gulp tasks system
    - Manage web app store using vuex
    - Implement image uploading and cropping
    - Integrate payment system using Stripe.
    - Build base CSS stylesheets

Skills
  • Languages
    Python, SCSS, PHP, Ruby, ECMAScript (ES6), JavaScript, HTML, CSS, SQL, TypeScript, Elixir, GraphQL
  • Frameworks
    Serverless Framework, Redux, Django, Ruby on Rails (RoR), AngularJS, Angular, Flux, Bootstrap 4, Bootstrap 3, Express.js, Flask, Django REST Framework, Vuetify.js, Angular Material, Protractor, Jasmine, OAuth2, Ampersand.js, Relay, Phoenix, Jest, React Native
  • Libraries/APIs
    Redux-saga, React.js, Socket.IO, Node.js, Vue.js, Ruby on Rails API, jQuery, Backbone.js, Vuex, Vue Material, React Router, React-redux, React Redux Form, Devise, Redux Form, MobX, Pundit, Material 2, Sidekiq, Reactstrap, Nokogiri, Flask-RESTful, Chai, SQLAlchemy, REST API, Nightwatch.js, D3.js, OmniAuth, RxJS, Facebook API
  • Tools
    Capistrano, Angular CLI, Git, Karma, Mocha, AWS ECS, Redux Thunk, VS Code, Grunt.js, Bundler, AWS SES, AWS VPC, Gulp.js, Webpack, pytest, RSpec, Cucumber, Logstash, AWS SDK, RabbitMQ, Auth0, Kibana, AWS SQS
  • Paradigms
    Test-driven Development (TDD), Functional Programming, Agile Software Development, Kanban, Behavior-driven Development (BDD), Scrum
  • Platforms
    Heroku, AWS Lambda, Mac OS, Red Hat Linux, Celery eCommerce, Linux, Ubuntu 16.04, Ubuntu 14.04, Firebase, Meteor
  • Storage
    AWS RDS, MySQL, PostgreSQL, MongoDB, Redis, AWS DynamoDB
  • Other
    AWS API Gateway, TSLint, ESLint, GitFlow, Elasticsearch, Vue-router, Bootstrap UI, Material-UI, RESTful Web Services, Enzyme, Apollo
Education
  • Bachelor's degree in Computer Science
    California State University - Los Angeles, California, USA
    2005 - 2008
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