How to Start Go Template Indexes from 1?

Custom Arithmetic Functions in Go Templates

In Go templates, the range action provides a convenient way to iterate through collections and access both the index and the element. However, the default index starts from 0. To achieve a more human-friendly numbering system starting from 1, a custom function can be defined.

Implementing the Custom Function

The key is to extend the template's built-in function map with a new function. In the example provided, the function is named "inc" and takes an integer as an argument. Within the function, a simple increment operation is performed.

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

Applying the Function in the Template

Once the custom function is defined, it can be invoked within the template using the following syntax:

{{inc $index}}, Text: {{element}}

This line calculates the incremented index and displays it as "Number:" before the actual element.

Example Usage

Consider an array of strings:

var strs []string
strs = append(strs, "test1")
strs = append(strs, "test2")

When the template is executed with this array, the output would look like:

Number: 1, Text: test1
Number: 2, Text: test2

Demonstrating the successful modification of the index values to start from 1 instead of 0.

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