How to Format Float Values in Go HTML Templates?

Format Float in Go Templates

Formatting float64 values in Go HTML templates can be done using multiple methods.

1. Pre-Format the Float

Format the float using fmt.Sprintf() before passing it to the template:

func main() {
  t := template.New("")
  data := map[string]interface{}{
    "value": strconv.FormatFloat(3.1415, 'f', 2, 32),
  }
  _ = t.Execute(os.Stdout, data) // Render the template with formatted value
}

2. Create a String() Function

Define a custom type with a String() method that formats the value to your liking:

type MyFloat struct {
  value float64
}

func (f MyFloat) String() string {
  return fmt.Sprintf("%.2f", f.value)
}

func main() {
  t := template.New("")
  data := map[string]interface{}{
    "value": MyFloat{3.1415},
  }
  _ = t.Execute(os.Stdout, data) // Render the template with custom type
}

3. Call printf() in Template

Call printf() in the template using a custom format string:

{{printf "%.2f" .value}}

4. Register a Custom Function

Register a custom function to simplify the formatting process:

tmpl := template.New("")
tmpl = tmpl.Funcs(template.FuncMap{
  "myFormat": func(f float64) string {
    return fmt.Sprintf("%.2f", f)
  },
})

func main() {
  data := map[string]interface{}{
    "value": 3.1415,
  }
  _ = tmpl.Execute(os.Stdout, data) // Render the template using custom function
}

In the template:

{{myFormat .value}}

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