How can I repeat HTML code multiple times in a Go web application using templates?

Repeating HTML Code Multiple Times in Go

In your Go web application, you have a need to output a specific HTML line numerous times, depending on the value of n.

Here's a way to approach this:

In HTML templates, the {{range}} action allows you to iterate over items. However, this action requires a slice, array, or map to work with.

Passing a Zero-Value Slice

To cater to this requirement, you can pass an empty slice with no allocated memory, such as make([]struct{}, n).

Template Code:

<ul>
{{range $idx, $e := .}}
    <li><a href="/?page={{$idx}}">{{$idx}}</a></li>
{{end}}
</ul>

Testing the Code:

tmpl := template.Must(template.New("").Parse(templ))
n := 5
if err := tmpl.Execute(os.Stdout, make([]struct{}, n)); err != nil {
    panic(err)
}

Output:

<ul>

    <li><a href="/?page=0">0</a></li>

    <li><a href="/?page=1">1</a></li>

    <li><a href="/?page=2">2</a></li>

    <li><a href="/?page=3">3</a></li>

    <li><a href="/?page=4">4</a></li>

</ul>

Using a Filled Slice

To customize the starting index for the links, you can fill the slice with specific values.

Template Code:

<ul>
{{range .}}
    <li><a href="/?page={{.}}">{{.}}</a></li>
{{end}}
</ul>

Example Test Code:

tmpl := template.Must(template.New("").Parse(templ))
n := 5
values := make([]int, n)
for i := range values {
    values[i] = (i + 1) * 2
}
if err := tmpl.Execute(os.Stdout, values); err != nil {
    panic(err)
}

Output:

<ul>

    <li><a href="/?page=2">2</a></li>

    <li><a href="/?page=4">4</a></li>

    <li><a href="/?page=6">6</a></li>

    <li><a href="/?page=8">8</a></li>

    <li><a href="/?page=10">10</a></li>

</ul>

Using a Custom Function

Finally, you can use a custom function within the templates to modify the index values as needed.

Template Code:

<ul>
{{range $idx, $e := .}}{{$idx := (Add $idx)}}
    <li><a href="/?page={{$idx}}">{{$idx}}</a></li>
{{end}}
</ul>

Custom Function:

func Add(i int) int {
    return i + 1
}

Output:

<ul>

    <li><a href="/?page=1">1</a></li>

    <li><a href="/?page=2">2</a></li>

    <li><a href="/?page=3">3</a></li>

    <li><a href="/?page=4">4</a></li>

    <li><a href="/?page=5">5</a></li>

</ul>

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