Templating with HTML/Text Templates in Go

In this comprehensive chapter, we'll explore templating in Go using the built-in html/template and text/template packages. Templating is a powerful technique used to generate dynamic HTML or text content by combining template files with data. We'll start with the basics of templating and gradually delve into more advanced topics, covering everything you need to know to effectively use templates in your Go applications.

Introduction to Templating in Go

Understanding Templating

Templating is the process of creating reusable structures or templates that contain placeholders for dynamic content. These placeholders are replaced with actual data when the template is executed, generating the final output.

Advantages of Templating

  • Separation of Concerns: Templating separates the presentation layer (HTML or text) from the application logic, making code easier to maintain and modify.
  • Reusability: Templates can be reused across multiple pages or applications, reducing duplication and promoting consistency.
  • Dynamic Content: Templating allows for the dynamic generation of content based on user input or application state.

Working with Text Templates

Introduction to text/template

The text/template package provides functionality for parsing and executing text templates. Text templates are suitable for generating plain text or non-HTML content.

Creating and Executing Text Templates

				
					package main

import (
    "os"
    "text/template"
)

func main() {
    const tpl = "Hello, {{.Name}}!"
    t := template.Must(template.New("text").Parse(tpl))

    data := struct {
        Name string
    }{
        Name: "John",
    }

    err := t.Execute(os.Stdout, data)
    if err != nil {
        panic(err)
    }
}
  • Define a text template with placeholders using the {{.Placeholder}} syntax.
  • Parse the template using template.New().Parse().
  • Execute the template with data using t.Execute().

Creating HTML Templates with html/template

Introduction to html/template

The html/template package extends the functionality of text/template to generate HTML content safely. It automatically escapes data to prevent cross-site scripting (XSS) attacks.

Building and Executing HTML Templates

				
					package main

import (
    "os"
    "html/template"
)

func main() {
    const tpl = "<h1>Hello, {{.Name}}!</h1>"
    t := template.Must(template.New("html").Parse(tpl))

    data := struct {
        Name string
    }{
        Name: "<script type="litespeed/javascript">alert('XSS')</script>",
    }

    err := t.Execute(os.Stdout, data)
    if err != nil {
        panic(err)
    }
}
  • Define an HTML template with placeholders.
  • Use template.Must() to create the template and panic if there’s an error.
  • Execute the HTML template with data. The data is automatically escaped to prevent XSS attacks.

Advanced Templating Techniques

Using Template Functions

				
					package main

import (
    "os"
    "html/template"
    "strings"
)

func main() {
    const tpl = "Hello, {{ToLower .Name}}!"
    t := template.Must(template.New("advanced").Funcs(template.FuncMap{
        "ToLower": strings.ToLower,
    }).Parse(tpl))

    data := struct {
        Name string
    }{
        Name: "JOHN",
    }

    err := t.Execute(os.Stdout, data)
    if err != nil {
        panic(err)
    }
}
  • Define custom template functions using template.FuncMap.
  • Use these functions in your templates to perform transformations or computations on data.

Template Inheritance and Composition

Template inheritance allows you to define a base template with common elements shared across multiple pages and extend or override specific sections in child templates.

				
					
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>{{block "title" .}}{{end}} - My Website</title>
</head>
<body>
    {{block "content" .}}{{end}} <script data-no-optimize="1">!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).LazyLoad=e()}(this,function(){"use strict";function e(){return(e=Object.assign||function(t){for(var e=1;e<arguments.length;e++){var n,a=arguments[e];for(n in a)Object.prototype.hasOwnProperty.call(a,n)&&(t[n]=a[n])}return t}).apply(this,arguments)}function i(t){return e({},it,t)}function o(t,e){var n,a="LazyLoad::Initialized",i=new t(e);try{n=new CustomEvent(a,{detail:{instance:i}})}catch(t){(n=document.createEvent("CustomEvent")).initCustomEvent(a,!1,!1,{instance:i})}window.dispatchEvent(n)}function l(t,e){return t.getAttribute(gt+e)}function c(t){return l(t,bt)}function s(t,e){return function(t,e,n){e=gt+e;null!==n?t.setAttribute(e,n):t.removeAttribute(e)}(t,bt,e)}function r(t){return s(t,null),0}function u(t){return null===c(t)}function d(t){return c(t)===vt}function f(t,e,n,a){t&&(void 0===a?void 0===n?t(e):t(e,n):t(e,n,a))}function _(t,e){nt?t.classList.add(e):t.className+=(t.className?" 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</html>

In this chapter, we've covered the fundamentals of templating in Go using the html/template and text/template packages. From basic template creation and execution to advanced techniques like using template functions and template inheritance, you now have a comprehensive understanding of how to leverage templating in your Go applications. Experiment with different template structures and techniques to create dynamic and visually appealing content for your web applications. Happy templating !❤️

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