Filter Reference¶

Filters are applied to values inside {{ }} tags using the pipe | operator. Multiple filters chain left-to-right.

{{ value | filter }}
{{ value | filter(arg) }}
{{ list | join(", ") | upper }}

String Filters¶

Filter	Signature	Description	Example
`lower`	`string → string`	Convert to lowercase	`{{ name \\| lower }}` → `acme`
`upper`	`string → string`	Convert to uppercase	`{{ name \\| upper }}` → `ACME`
`trim`	`string → string`	Strip leading/trailing whitespace	`{{ value \\| trim }}`
`length`	`string → number`	Number of characters	`{{ name \\| length }}` → `4`
`default(val)`	`any → any`	Return `val` if input is falsy/undefined	`{{ desc \\| default("N/A") }}`

Filter	Signature	Description	Example
`length`	`array → number`	Number of items	`{{ items \\| length }}`
`join(sep)`	`array → string`	Join items with separator (default: `""`)	`{{ tags \\| join(", ") }}`
`first`	`array → any`	First element	`{{ releases \\| first }}`
`last`	`array → any`	Last element	`{{ releases \\| last }}`
`reverse`	`array → array`	Reverse order	`{{ items \\| reverse }}`
`sort`	`array → array`	Lexicographic sort	`{{ names \\| sort }}`
`unique`	`array → array`	Remove duplicate values	`{{ tags \\| unique }}`
`default(val)`	`array → array`	Return `val` if input is empty/undefined	`{{ list \\| default([]) }}`

@inputs
tags: string[] = []

<tag-line>
Tags: {{ tags | sort | unique | join(", ") }}

Input ["beta", "api", "beta", "stable"] renders:

Tags: api, beta, stable

Filters can be used inside {% if %} conditions:

{% if added | length > 0 -%}
### Added
{% for item in added -%}
- {{ item }}
{% endfor -%}
{% endif %}

The expression added | length > 0 pipes added through the length filter, then compares the result to 0.