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Hiccup
Hiccup is a library for representing HTML in Clojure. It uses vectors
to represent elements, and maps to represent an element's attributes.
Install
Add the following dependency to your deps.edn file:
hiccup/hiccup {:mvn/version "2.0.0"}
Or to your Leiningen project.clj file:
[hiccup "2.0.0"]
Documentation
Wiki
API Docs
Syntax
Here is a basic example of Hiccup syntax:
user=> (require '[hiccup2.core :as h])
nil
user=> (str (h/html [:span {:class "foo"} "bar"]))
"<span class=\"foo\">bar</span>"
The first element of the vector is used as the element name. The second
attribute can optionally be a map, in which case it is used to supply
the element's attributes. Every other element is considered part of the
tag's body.
Hiccup is intelligent enough to render different HTML elements in
different ways, in order to accommodate browser quirks:
user=> (str (h/html [:script]))
"<script></script>"
user=> (str (h/html [:p]))
"<p />"
And provides a CSS-like shortcut for denoting id and class
attributes:
user=> (str (h/html [:div#foo.bar.baz "bang"]))
"<div id=\"foo\" class=\"bar baz\">bang</div>"
If the body of the element is a seq, its contents will be expanded out
into the element body. This makes working with forms like map and
for more convenient:
user=> (str (h/html [:ul
(for [x (range 1 4)]
[:li x])]))
"<ul><li>1</li><li>2</li><li>3</li></ul>"
Strings are automatically escaped:
user=> (str (h/html [:p "Tags in HTML are written with <>"]))
"<p>Tags in HTML are written with <></p>"
To bypass this, use the hiccup2.core/raw function:
user=> (str (h/html [:p (h/raw "Hello <em>World</em>")]))
"<p>Hello <em>World</em></p>"
This can also be used for doctype declarations:
user=> (str (h/html (h/raw "<!DOCTYPE html>") [:html {:lang "en"}]))
"<!DOCTYPE html><html lang=\"en\"></html>"
Differences between Hiccup 1 and 2
In brief: Hiccup 1 doesn't escape strings by default, while Hiccup 2
does. They occupy different namespaces to ensure backward compatibility.
In Hiccup 1, you use the h function to escape a string - that is,
ensure that unsafe characters like <, > and & are converted into
their equivalent entity codes:
(h1/html [:div "Username: " (h1/h username)])
In Hiccup 2 strings are escaped automatically, but the return value from
the html macro is a RawString, rather than a String. This ensures
that the html macro can still be nested.
(str (h2/html [:div "Username: " username]))
It's recommended to use Hiccup 2 where possible, particularly if your
app handles user data. Use of the non-core namespaces, such as
hiccup.page, should be avoided with Hiccup 2.
License
Copyright © 2025 James Reeves
Distributed under the Eclipse Public License either version 1.0 or (at
your option) any later version.
Read the full README on GitHub
