react fundamentals - jakarta js, apr 2016
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REACT FUNDAMENTALSJAKARTA JS
Simon Sturmer : @sstur_
CTO / Fouder - KodeFox
WHAT IS REACT?
▸ So you've heard the hype, but what is React?
▸ React is an opinionated View library.
▸ It is a fundamentally different way to build UIs.
▸ It leads to thinking in terms of pure functions and immutability and other good practices.
▸ Why are so many top companies choosing React?
▸ Netflix, Yahoo, Apple, AirBnB, WhatsApp, CloudFlare, Dropbox, Instagram, Twitter, Uber, WordPress even SaleStock Indonesia
▸ Performance, Testability, Code Reuse
▸ Developer Experience.
▸ How is React different from Angular/Ember/etc?
▸ Everything is a component.
▸ A component is a pure function of application state.
▸ Components can be reused, composed to create other components, isolated for testing.
▸ UI is easy to reason about as state changes over time.
REACT IS A BUSINESS DECISION, NOT JUST A TECHNOLOGY CHOICE!
REACT AS A BUSINESS DECISION
▸ Fewer, more versatile software engineers!
▸ Same dev team! Web, iOS, Android, Desktop
▸ Improved Testability, Reliability
▸ Performant by Default
▸ Real Code Reuse
▸ Velocity: shorten the edit-reload cycle; less time debugging
▸ Future proof: As your software evolves, replace individual components.
WHY BUSINESSES STILL CHOOSE ANGULAR/EMBER?
▸ New tech can be overwhelming. Where to start?
▸ How to train your dev team?
▸ Some have large, legacy code-bases with a lot of resources invested.
HOW IS REACT DIFFERENT?
WHAT PROBLEM DOES REACT TRY TO SOLVE?
▸ App state changing over time is hard to reason about.
▸ UI components get out of sync with each other and it's hard to debug.
▸ When changes happen, we have to reach deep into our view and mutate objects.
SHARED MUTABLE STATE IS THE ROOT OF ALL EVIL
Pete Hunt, React.js Conf 2015
REACT + REDUX GIVES YOU IMMUTABLE STATE
REMEMBER THE OLD DAYS?
▸ Server-side Rendering
▸ Generating HTML views was easy!
▸ Why? … because we had the full application state at one moment in time (a snapshot)
▸ All we have to do is query stuff and generate HTML from that stuff.
▸ When an action happens, re-generate the entire view!
SPRINKLING JS ON TOP
▸ Web apps slowly started doing more client-side
▸ DOM Manipulation: jQuery
▸ Client-side templating: mustache, handlebars
▸ Must wire-up events every time you generate new DOM
▸ Still need to manipulate the DOM!
EVENTS UPDATING VIEW
▸ There's way too much complexity around keeping your app in a consistent state.
▸ It's almost impossible to reason about.
▸ The bookkeeping makes for a poor developer experience.
▸ We never had that problem with server-side rendering!
▸ … because we just re-generated the entire view when a piece of state changed (url change).
▸ Can we do the same thing client-side?
CLIENT-SIDE FULL RE-RENDER
EVENTS UPDATING STATE
THAT'S EXACTLY HOW REACT WORKS.
VIEW IS A FUNCTION OF STATE:
▸ This means you can reason about your view just like you used to do with server-generated views.
▸ Your view is a deterministic function of your state.(the same state will always produce the same view)
▸ Even if you serialize that state, save it to disk and restore it next week.
MORE EXCELLENTTHINGS WILL FOLLOW
Once you start down this path…
YOU START DISCOVERING BONUS STUFF LIKE:
▸ Trivial undo/redo
▸ Easy hot-reloading during development
▸ Atomic/Optimistic updates
▸ Imagine if an HTTP request fails, you just load a previously stable state
▸ Time-travel debugging
▸ Imagine stepping back in time through your app state
LET'S LOOK ATSOME REACT CODE…
REACT VERSION OF PREVIOUS EXAMPLE
EVENTS JUST UPDATE STATE!
…but there are <div>s in your JS!
IN REALITY IT WILL LOOK MORE LIKE THIS:
▸ That stuff is JSX and it’s really incredible
▸ It looks weird at first, but it is just [optional] sugar.
▸ Concise Syntax
▸ Static code analysis
▸ Directly compiles to JS
COMPOSITION OF COMPONENTS
▸ You build view components from other view components
▸ This is extremely powerful.
▸ Code Reuse
▸ Separation of Concerns
▸ Clean layers of abstraction
React leaves it up to you to separate concerns however you like.
MOST PEOPLE HAVE:
▸ Presentational components:
▸ Purely for layout/styling
▸ CSS designers can work on these
▸ Container components:
▸ Know about data structure and logic
▸ Don’t know anything about layout/styling
So what's the price you pay for using React?
▸ Some setup complexity. Choices can be overwhelming.
▸ A moderate learning curve
▸ React will change the way you think about your UI. This takes some getting used to.
▸ Rapidly evolving ecosystem.
VASTLY OUTWEIGHS THE COST.
But what you get in return…
▸ Move fast: shorten the edit-reload cycle; spend less time debugging
▸ Write testable code!
▸ Iterate with confidence and build more reliable software.
▸ Learn once, write anywhere
▸ Web, iOS, Android, Mac/Windows, even console apps