How to Use If-Else and Switch Loop Inside HTML Template in Golang

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Jay Singh Feb 02, 2024
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  1. Use the if-else Loop Inside HTML Templates in Golang
  2. Use the switch Loop Inside HTML Template in Golang
How to Use If-Else and Switch Loop Inside HTML Template in Golang

HTML template is a Golang (Go) package that supports data-driven templates for creating secure HTML outputs against code injection. One significant advantage of utilizing HTML/template is that it generates safe, escaped HTML output using contextual auto-escaping.

As a result, anytime the output is HTML, the HTML template package should always be used instead of a text template. Let’s look at a few examples of utilizing if-else and switch in the HTML template.

Use the if-else Loop Inside HTML Templates in Golang

In this example, we create two structs to hold the data from our ToDo list items: ToDo and PageData. The defined HTML template, tmpl, is created and parsed.

Finally, we render our HTML by giving it to the Execute() function, the data, and the parsed HTML template.

Code:

package main

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

type Todo struct {
	Title string
	Done  bool
}

type PageData struct {
	PageTitle string
	Todos     []Todo
}

func main() {
	const tmpl = `
    <h1>{{.PageTitle}}</h1>
    <ul>
        {{range .Todos}}
            {{if .Done}}
                <li>{{.Title}} &#10004</li>
            {{else}}
                <li>{{.Title}}</li>
            {{end}}
        {{end}}
    </ul>`
	t, err := template.New("webpage").Parse(tmpl)
	if err != nil {
		log.Fatal(err)
	}
	data := PageData{
		PageTitle: "Personal TODO list",
		Todos: []Todo{
			{Title: "Task 1", Done: true},
			{Title: "Task 2", Done: false},
			{Title: "Task 3", Done: false},
		},
	}
	t.Execute(os.Stdout, data)
}

Output:

Personal TODO list
Task 1 ✔
Task 2
Task 3

Use the switch Loop Inside HTML Template in Golang

Code:

package main

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

func main() {
	const (
		paragraph_hypothesis = 1 << iota
		paragraph_attachment = 1 << iota
		paragraph_menu       = 1 << iota
	)

	const text = "{{.Paratype | printpara}}\n"

	type Paragraph struct {
		Paratype int
	}

	var paralist = []*Paragraph{
		&Paragraph{paragraph_hypothesis},
		&Paragraph{paragraph_attachment},
		&Paragraph{paragraph_menu},
	}

	t := template.New("testparagraphs")

	printPara := func(paratype int) string {
		text := ""
		switch paratype {
		case paragraph_hypothesis:
			text = "This is a hypothesis testing\n"
		case paragraph_attachment:
			text = "This is using switch case\n"
		case paragraph_menu:
			text = "Menu\n1:\n2:\n3:\n\nPick any option:\n"
		}
		return text
	}

	template.Must(t.Funcs(template.FuncMap{"printpara": printPara}).Parse(text))

	for _, p := range paralist {
		err := t.Execute(os.Stdout, p)
		if err != nil {
			fmt.Println("executing template:", err)
		}
	}
}

Output:

This is a hypothesis testing

This is using switch case

Menu
1:
2:
3:

Pick any option: