There are 6 difficult problems frameworks and libraries try to solve in JavaScript, but never quite get there. Learn how these problems (and more!) are solved by ClojureScript and how it can provide a platform for new solutions.

1. ClojureScript:
I can't believe this is
JavaScript
Eric Normand

2. Clojure transpiled to
JavaScript

3. ClojureScript
I can’t believe this is JavaScript!

4. For the video and transcript
of this presentation,
click here:
https://lispcast.com/clojurescript-cant-believe-javascript/

5. Callback Hell

6. Callback Hell
• JavaScript uses callback-style for async
• Not just about indentation
• About inversion of control
• I don’t know when or in what order or even if
my code will be called!

7. JavaScript vs Callback hell
• Promises
• Helps a lot!
• Still have promises within promises within
promises
• async/await
• nice!
• Together: wow, a really good solution!

8. ClojureScript vs Callback Hell
• core.async
• A library that turns sequential code into
callbacks
• Never give up control
• Based on Communicating Sequential Processes
• (the same thing Go is based on)

9. Code Optimization

10. Code Optimization
• Milliseconds === $$$$
• Minify code
• Remove dead code
• Split code

11. JavaScript vs Optimization
• webpack
• minification
• dead code elimination
• splitting
• Rollup
• tree shaking

12. ClojureScript vs Optimization
• Google Closure Compiler
• heavily tested
• optimizes Gmail
• “just works”

13. Stateful DOM

14. Stateful DOM
• Dynamic apps need to modify the DOM
• DOM and your data get out of sync

15. JavaScript vs DOM
• JavaScript sprinkles
• Just use JS for making small improvements to a static page
• Angular/Ember
• Make a new HTML that is responsive to changes to state
• React
• Build new components that manage their view state
• Vue

16. ClojureScript vs DOM
• React
• Re-frame, Om, Rum — Basically just the Virtual DOM
• Manage app state in one place, View in another
• Really fast
• Very functional
• Hoplon
• Spreadsheet cells for changes

17. Application State Management

18. Application State
• Applications have a lot data to keep track of
• It’s hard to tell what has changed and when
• It’s hard to keep in synch with the server

19. JavaScript vs State
• Mutable objects and variables
• Component state
• Redux
• Immutable.js
• GraphQL
• Falcor

20. ClojureScript vs State
• One mutable variable with immutable data
• Re-frame + Om Next
• Redux was inspired by these
• Manage their own “databases”
• Encourage a “pull model” with the server

21. Build tool fatigue

22. Build tool fatigue
• There’s a lot of stuff a modern project needs
• linting
• transpiling
• dependency management
• bundling

23. JavaScript vs Tools
• Many options
• Webpack
• Grunt
• Gulp
• Browserify
• NPM
• Rollup
• These are just the bundlers!!
• No clear winner
• Broken promises
• Bad documentation

24. ClojureScript vs Tools
• Leiningen
• Configuration / declarative
• Plugins
• Boot
• Procedural / task-based
• Libraries

25. Development flow

26. Development flow
• Web development is very visual
• We want to see changes right away

27. JavaScript vs Flow
• “Plain” flow
• Save changes to JS + CSS.
• Watcher recompiles on change.
• Reload the browser.
• Click around to where you were in your app.
• Hot Module Reloading
• Save changes to JS + CSS.
• Watcher recompiles on change.
• Watcher sends new code to browser.
• Works for some applications.

28. ClojureScript vs Flow
• Figwheel
• Compiles ClojureScript and sends it to browser
• See changes in less than a second
• Application state is untouched

29. Extra slides

30. Embrace the host

31. Built-in

32. Platforms

33. React

34. Other Goodies

35. Module Systems

36. core.async

37. EDN

38. Google Closure Compiler

39. Eric Normand
Follow Eric on:
Eric Normand @EricNormand
eric@lispcast.comlispcast.com