mirror of https://github.com/status-im/reagent.git
169 lines
5.2 KiB
Markdown
169 lines
5.2 KiB
Markdown
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# Reagent
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A simple [ClojureScript](http://github.com/clojure/clojurescript) interface to [React](http://facebook.github.io/react/).
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Reagent provides a way to write efficient React components using (almost) nothing but plain ClojureScript functions.
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* **[Detailed intro with live examples](http://reagent-project.github.io/)**
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* **[News](http://reagent-project.github.io/news/index.html)**
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* **[API Documentation](http://reagent-project.github.io/docs/master/)**
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* **Community discussion and support channels**
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* **[#reagent](https://clojurians.slack.com/messages/reagent/)** channel in [Clojure Slack](http://clojurians.net/)
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* **[Reagent Project Mailing List](https://groups.google.com/forum/#!forum/reagent-project)**
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### Prerequisites
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* Java JDK
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* [Leiningen](http://leiningen.org/)
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### Usage
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To create a new Reagent project simply run:
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lein new reagent myproject
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If you wish to only create the assets for ClojureScript without a Clojure backend then do the following instead:
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lein new reagent-frontend myproject
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This will setup a new Reagent project with some reasonable defaults, see here for more [details](https://github.com/reagent-project/reagent-template).
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To use Reagent in an existing project you add this to your dependencies in `project.clj`:
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[](http://clojars.org/reagent) <br>
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[](https://circleci.com/gh/reagent-project/reagent)
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This is all you need to do if you want the standard version of React. If you want the version of React with addons, you'd use something like this instead:
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[reagent "0.7.0" :exclusions [cljsjs/react]]
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[cljsjs/react-with-addons "15.4.2-2"]
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If you want to use your own build of React (or React from a CDN), you have to use `:exclusions` variant of the dependency, and also provide a file named "cljsjs/react.cljs", containing just `(ns cljsjs.react)`, in your project.
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## Examples
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Reagent uses [Hiccup-like](https://github.com/weavejester/hiccup) markup instead of React's sort-of html. It looks like this:
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```clj
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(defn some-component []
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[:div
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[:h3 "I am a component!"]
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[:p.someclass
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"I have " [:strong "bold"]
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[:span {:style {:color "red"}} " and red"]
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" text."]])
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```
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Reagent extends standard Hiccup in one way: it is possible to "squeeze" elements together by using a `>` character.
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```clj
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[:div
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[:p
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[:b "Nested Element"]]]
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```
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can be written as:
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```clj
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[:div>p>b "Nested Element"]
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```
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> **Since version 0.8:** The `:class` attribute also supports collections of classes, and nil values are removed:
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>
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> ```clj
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> [:div {:class ["a-class" (when active? "active") "b-class"]}]
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> ```
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You can use one component inside another:
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```clj
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(defn calling-component []
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[:div "Parent component"
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[some-component]])
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```
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And pass properties from one component to another:
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```clj
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(defn child [name]
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[:p "Hi, I am " name])
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(defn childcaller []
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[child "Foo Bar"])
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```
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You mount the component into the DOM like this:
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```clj
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(defn mountit []
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(r/render [childcaller]
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(.-body js/document)))
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```
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assuming we have imported Reagent like this:
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```clj
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(ns example
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(:require [reagent.core :as r]))
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```
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State is handled using Reagent's version of `atom`, like this:
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```clj
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(defonce click-count (r/atom 0))
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(defn state-ful-with-atom []
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[:div {:on-click #(swap! click-count inc)}
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"I have been clicked " @click-count " times."])
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```
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Any component that dereferences a `reagent.core/atom` will be automatically re-rendered.
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If you want do some setting up when the component is first created, the component function can return a new function that will be called to do the actual rendering:
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```clj
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(defn timer-component []
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(let [seconds-elapsed (r/atom 0)]
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(fn []
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(js/setTimeout #(swap! seconds-elapsed inc) 1000)
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[:div
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"Seconds Elapsed: " @seconds-elapsed])))
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```
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This way you can avoid using React's lifecycle callbacks like `getInitialState` and `componentWillMount` most of the time.
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But you can still use them if you want to, either using `reagent.core/create-class` or by attaching meta-data to a component function:
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```clj
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(defonce my-html (r/atom ""))
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(defn plain-component []
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[:p "My html is " @my-html])
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(def component-with-callback
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(with-meta plain-component
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{:component-did-mount
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(fn [this]
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(reset! my-html (.-innerHTML (reagent/dom-node this))))}))
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```
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See the examples directory for more examples.
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## Performance
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React is pretty darn fast, and so is Reagent. It should even be faster than plain old javascript React a lot of the time, since ClojureScript allows us to skip a lot of unnecessary rendering (through judicious use of React's `shouldComponentUpdate`).
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The ClojureScript overhead is kept down, thanks to lots of caching.
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Code size is a little bigger than React.js, but still quite small. The todomvc example clocks in at roughly 79K gzipped, using advanced compilation.
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## About
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The idea and some of the code for making components atom-like comes from [pump](https://github.com/piranha/pump). The reactive-atom idea (and some code) comes from [reflex](https://github.com/lynaghk/reflex).
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The license is MIT.
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