Template extensions

The globals and filters plugin options let you extend the Nunjucks template environment with custom functions and filters. Both are available across all form page templates and in page templates (LiquidJS).

Globals

Globals are functions you call directly in templates, without needing an input value. Register them via the globals plugin option:

await server.register({
  plugin,
  options: {
    globals: {
      getCurrentYear: () => new Date().getFullYear(),
      formatCurrency: (amount) =>
        new Intl.NumberFormat('en-GB', {
          style: 'currency',
          currency: 'GBP'
        }).format(amount)
    }
  }
})

Use them in any Nunjucks template:

<p>Copyright {{ getCurrentYear() }}</p>
<p>Total: {{ formatCurrency(123.45) }}</p>

Filters

Filters transform a value passed on the left side of the | operator. Register them via the filters plugin option:

const formatter = new Intl.NumberFormat('en-GB')

await server.register({
  plugin,
  options: {
    filters: {
      money: (value) => formatter.format(value),
      upper: (value) => (typeof value === 'string' ? value.toUpperCase() : value)
    }
  }
})

Use them in any Nunjucks template, or in LiquidJS page templates:

<p>{{ amount | money }}</p>
<p>{{ name | upper }}</p>

Built-in filters

forms-engine-plugin registers several filters automatically. These are available in all templates without any configuration:

Filter	Description
`markdown`	Renders a Markdown string to HTML
`answer`	Returns the user's answer for a given component name (LiquidJS only)
`page`	Returns the page definition for a given path (LiquidJS only)
`field`	Returns the component definition for a given name (LiquidJS only)
`href`	Returns the full page href for a given path (LiquidJS only)
`evaluate`	Evaluates a nested LiquidJS template using the current context (LiquidJS only)

The LiquidJS-only filters are documented in full in Page templates.