How to Print a Period After the Last Array Item in a Go Template?

Detecting the Last Array Item in a Go Template

When iterating over an array in a Go template, a common problem is printing a comma after each element. This can be undesirable when displaying the last element, where a period would be a more suitable ending character.

In the provided code, the template {{range $i, $el := .items}}{{$el}},{{end}} iterates over the items array and prints each element followed by a comma. To print a period after the last element, we need to modify the template.

The solution involves using the if statement to conditionally include the comma. Here's the modified template:

<code class="go">tpl := "{{range $i, $el := .items}}{{if $i}},{{end}}{{$el}}{{end}}."</code>

In this template:

• The {{range $i, $el := .items}} part remains the same.
• We add an if $i statement that checks if $i is greater than zero. This condition is true for all elements except the first one.
• If $i is greater than zero, we print a comma.
• We print {{$el}} to output the element.
• We end the range with {{end}}.
• We append a period character at the end of the template.

With this template, the program will print the following:

1,4,2.

The last element is correctly ended with a period. This technique of conditionally printing separators is a useful trick for formatting output in Go templates.

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