Reagent uses a datastructure known as Hiccup to describe HTML. Hiccup describes HTML elements and user-defined components as a nested ClojureScript vector:
[:div {:class "parent"}
[:p {:id "child-one"} "I'm first child element."]
[:p "I'm the second child element."]]
As described below, reagent provides a number of extensions and conveniences to Hiccup, but the general rules of Hiccup are as follows:
(name keyword)
is the tag of the HTML element.nil
child nodesReagent and React ignore nil nodes, which allow conditional logic in Hiccup forms:
(defn my-div [child?]
[:div
"Parent Element"
(when child? [:div "Child element"])])
In this example (my-div false)
will evaluate to [:div "Parent Element" nil]
, which reagent will simply treat the same as [:div "Parent Element"]
.
style
attributeThe :style
attribute can be written a string or as a map. The following two are equivalent:
[:div {:style "color: red; font-weight: bold"} "Alert"]
[:div {:style {:color "red"
:font-weight "bold"}
"Alert"]
The map form is the same as React's style attribute, except that when using the map form of the style attribute, the keys should be the same as the CSS attribute as shown in the example above (not in camel case as is required JavaScript).
class
attributeIn JavaScript, class
is a reserved keyword, so React uses the className
to specify class attibutes. Reagent just uses class
.
As of reagent 0.8.0, the class
attribute accepts a collection of classes and will remove any nil value:
[:div {:class ["a-class" (when active? "active") "b-class"]}]
The id of an element can be indicated with a hash (#
) after the name of the element.
This:
[:div#my-id]
is the same as this:
[:div {:id "my-id"}]
One or more classes can be indicated for an element with a .
and the class-name like this:
[:div.my-class.my-other-class.etc]
which is the same as:
[:div {:class ["my-class" "my-other-class" "etc"]}]
Special notations for id and classes can be used together. The id must be listed first:
[:div#my-id.my-class.my-other-class]
which is the same as:
[:div {:id "my-id" :class ["my-class" "my-other-class"]}]
Reagent extends standard Hiccup in one way: it is possible to stack elements together by using a >
character.
This:
[:div
[:p
[:b "Nested Element"]]]
can be written as:
[:div>p>b "Nested Element"]
The primary entrypoint to the reagent library is reagent.dom/render
.
(ns example
(:require [reagent.dom :as rdom]))
(defn render-simple []
(rdom/render [:div [:p "Hello world!"]]
(.-body js/document)))
This render
function expects one of two things:
If it encounters a ClojureScript vector, it will interpret it as Hiccup. Reagent expects one of two things in the first position of the vector:
:div
or :span
, which it will create using React.createElementmy-component
.If it's a symbol, then reagent will evaluate a function by that name. Reagent expects one of three things from this function:
reagent.core/create-class
or it could be a React component you have imported from a JavaScript library.Can you improve this documentation? These fine people already did:
Juho Teperi, Dominic Freeston, Iyed Bennour & Mikkel GravgaardEdit on GitHub
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