tags: A small DSL for building HTML documents

Installation

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CentOS/RHEL 7 or Amazon Linux 2

yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install lua-resty-tags

CentOS/RHEL 8+, Fedora Linux, Amazon Linux 2023

yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install lua5.1-resty-tags

To use this Lua library with NGINX, ensure that nginx-module-lua is installed.

This document describes lua-resty-tags v1.0 released on Jul 06 2016.

A small DSL for building HTML documents

Synopsis

Here we define some local functions:

local tags = require "resty.tags"
local html,   head,   script,   body,   h1,   p,   table,   tr,   th,   img,   br = tags(
     "html", "head", "script", "body", "h1", "p", "table", "tr", "th", "img", "br")

print(
    html { lang = "en" } (
        head (
            script { src = "main.js" }
        ),
        body (
            h1 { class = 'title "is" bigger than you think', "selected" } "Hello",
            h1 "Another Headline",
            p (
                "<Beautiful> & <Strange>",
                br,
                { Car = "Was Stolen" },
                "Weather"
            ),
            p "A Dog",
            img { src = "logo.png" },
            table(
                tr (
                    th { class = "selected" } "'Headline'",
                    th "Headline 2",
                    th "Headline 3"
                )
            )
        )
    )
)

The above will output HTML similar to:

<html lang="en">
    <head>
        <script src="main.js"></script>
    </head>
    <body>
        <h1 class="title &quot;is&quot; bigger than you think" selected>
            Hello
        </h1>
        <h1>
            Another Headline
        </h1>
        <p>
            &lt;Beautiful&gt; &amp; &lt;Strange&gt;
            <br>
            table: 0x0004c370Weather
        </p>
        <p>
            A Dog
        </p>
        <img src="logo.png">
        <table>
            <tr>
                <th class="selected">
                    &#39;Headline&#39;
                </th>
                <th>
                    Headline 2
                </th>
                <th>
                    Headline 3
                </th>
            </tr>
        </table>
    </body>
</html>

Here we pass in a function:

local tags = require "resty.tags"
local html = tags(function()
    return html { lang = "en"} (
        head (
            script { src = "main.js" }
        ),
        body (
            h1 { class = 'title "is" bigger than you think', "selected" } "Hello",
            h1 "Another Headline",
            p (
                "<Beautiful> & <Strange>",
                br,
                { Car = "Was Stolen" },
                "Weather"
            ),
            p "A Dog",
            img { src = "logo.png" },
            table(
                tr (
                    th { class = "selected" } "'Headline'",
                    th "Headline 2",
                    th "Headline 3"
                )
            )
        )
    )
end)
print(html())

And the output is similar:

<html lang="en">
    <head>
        <script src="main.js"></script>
    </head>
    <body>
        <h1 class="title &quot;is&quot; bigger than you think" selected>
            Hello
        </h1>
        <h1>
            Another Headline
        </h1>
        <p>
            &lt;Beautiful&gt; &amp; &lt;Strange&gt;
            <br>
            table: 0x00054ce0Weather
        </p>
        <p>
            A Dog
        </p>
        <img src="logo.png">
        <table>
            <tr>
                <th class="selected">
                    &#39;Headline&#39;
                </th>
                <th>
                    Headline 2
                </th>
                <th>
                    Headline 3
                </th>
            </tr>
        </table>
    </body>
</html>

In this example we create a table snippet:

local tags = require "resty.tags"
local table = tags(function(rows)
    local table = table
    for _, row in ipairs(rows) do
        local tr = tr
        for _, col in ipairs(row) do
            tr(td(col))
        end
        table(tr)
    end
    return table
end)

print(table{
    { "A", 1, 1 },
    { "B", 2, 2 },
    { "C", 3, 3 }
})

And here is the output of it:

<table>
    <tr>
        <td>A</td>
        <td>1</td>
        <td>1</td>
    </tr>
    <tr>
        <td>B</td>
        <td>2</td>
        <td>2</td>
    </tr>
    <tr>
        <td>C</td>
        <td>3</td>
        <td>3</td>
    </tr>
</table>

Some special treatment is done to `<script>` and `<style>` tags:

local tags = require "resty.tags"
local script = tags("script")
print(script[[
    function hello() {
        alert("<strong>Hello World</strong>");
    }
    hello();
]])

As you can see, we don't HTML encode the output:

<script>
    function hello() {
        alert("<strong>Hello World</strong>");
    }
    hello();
</script>

License

lua-resty-tags uses two clause BSD license.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES`

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-tags.