doublebrace - additional functions for Go templates

The default functions in text/template and html/template are minimal. This extends them.

Quick Start

Requires Go >= 1.23.

import (
	"github.com/client9/doublebrace"
)

t := template.New("foo").Funcs(doublebrace.FuncMap())

What's Included?

• strings — case, trim, search, replace, split/join, truncate, rune-aware length
• math — arithmetic, rounding, min/max, clamp, pow
• cast — toInt, toFloat for frontmatter values that arrive as strings
• encoding — jsonify for embedding data in <script> blocks
• date and time — now, parseTime; use time.Time methods for formatting
• url / safe types — urlEncode, urlPathEscape, safeHTML, safeCSS, etc.
• path — pathBase, pathDir, pathExt, pathJoin, pathClean
• lists (slices) — list, seq, take, drop, sort, sortNum, reverse, concat, …
• dicts (maps) — dict, keys, values, merge

Goals

• Independent and exportable — serves as a base, or for use in different templating systems
• Stdlib only — keep it simple; functions requiring external deps go in a different module
• Not pipeline-based — pipeline order looks elegant for single-argument functions, then gets confusing. Argument order follows Go stdlib (subject first).
• Prefer separate functions over extra arguments — sort and sortNum instead of a mode flag
• Immutable data structures — all functions return new values, never modify inputs

Alternatives

Masterminds/sprig — appears semi-abandoned, pipeline-based, has a number of unusual functions and dependencies.

Hugo — the static site generator has many functions, but inconsistent design and argument order optimized for pipelines. Implementation is tightly coupled to Hugo internals.

Not Included

• Internationalization / titlecase — requires golang.org/x/text; good for a separate module. Note: all string operations here are rune-aware.
• Regular expressions — defer until use cases in templates are better understood
• Base64 encoding — two competing encodings (standard vs URL-safe); add when use case is clear
• Random / shuffle — non-deterministic output is problematic for static site generators.
• Checksum and hashes — limited uses, many variations; good for a separate module
• Cryptography — limited use, many variations,
• OS and environment — pass these as data to the template instead
• Math trig — limited utility in HTML templates