Template Engine

scaffdog uses the template engine inpired by ECMAScript and Go text/template.
It has its own syntax and runtime to enhance the readability and writing quality of the templates 🐶

If you need a syntax specification, see the Language Specification section.

Basic Syntax#

Between {{ and }} is interpreted as a tag. Whitespace in tag contents is ignored.

{{ <statement> }}

{{ inputs.value }}
{{ null }}
{{ undefined }}
{{ true }}
{{ false }}
{{ 10 }}
{{ 2 + 3 }}
{{ "string" }}

Output:

foo-bar




10
5
string

Comments#

You can use comment out to keep the template readable. Of course, it is not deployed as a template.

{{ /* a comment */ }}

Call Helper Function#

Execute the helper function with the specified name. Arguments are separated by whitespace.
When invoked on a pipe, the previous processing result is passed to the first argument.

See the Built-in Helpers section for the helpers that can be used.

{{ <helper> <argument> ... }}
or
{{ <helper>(<argument>, [...]) }}

Example:

{{ relative "../" }}
{{ len(inputs.value) }}
{{ replace(inputs.value, "-", "") }}

Pipelines#

You can chain output values or helper results with pipes.

{{ <expression> | <helper> }}
{{ <expression> | <helper> <argument> ... }}

Example:

{{ inputs.value | upper }}
{{ inputs.value | replace ".ts$" ".js" | pascal }}
{{ output.base | replace output.ext ".js" | pascal }}

Grouping Operator#

The grouping operator ( ) controls the precedence of evaluation in expressions.

{{ (<expression>) }}

Example:

{{ 2 * (2 + 2) }}
{{ 5 + (inputs.value | camel | len) }}

Ternary Operator#

Ternary operators are supported to branch the result based on the result of evaluation of boolean values.

{{ <expression> ? <expression> : <expression> }}

{{ 1 != 2 ? "a" : "b" }}
{{ 2 > 5 ? "a" : "b" }}

Output:

a
b

Local Variables#

You can define local variables in your templates.
The left and right sides are connected by a := token, which assigns to the left side the value of the right side evaluation. Also, variable assignment statements do not produce output.

{{ <identifier> := <expression> }}

Example:

{{ name := "scaffdog" }}
{{ name := inputs.name | camel }}

Conditional Branch#

An if statement can be used to perform conditional branching. The if statement must always be closed with end.
Cases where the condition does not apply can be written in the statement following else.

{{ if <expression> }}body{{ end }}
{{ if <expression> }}body{{ else }}body{{ end }}
{{ if <expression> }}body{{ else if <expression> }}body{{ end }}
{{ if <expression> }}body{{ else if <expression> }}body{{ else }}body{{ end }}

Example:

{{ if len(inputs.value) > 5 }}Long{{ end }}
{{ if len(inputs.value) > 5 }}Long{{ else }}Not long{{ end }}
{{ if len(inputs.value) > 5 }}Long{{ else if len(inputs.value) > 2 }}Medium{{ end }}
{{ if len(inputs.value) > 5 }}Long{{ else if len(inputs.value) > 2 }}Medium{{ else }}Short{{ end }}

For-loop#

Supports for statements to output repeated array values. The for statement must always be closed with end.
Use continue to skip iterations based on conditions, or break to skip the entire iteration.

You can also refer to an index by following the array value with a , token.

{{ for <identifier> in <expression> }}body{{ end }}
{{ for <identifier>, <identifier> in <expression> }}body{{ end }}

{{ for v in seq 1 5 }}{{ v }}{{ end }}
{{ for v, i in seq 1 5 }}{{ v + i }}{{ end }}

{{- /* continue and break */ }}
{{ for v in seq 1 5 }}{{ if v == 2 }}{{ continue }}{{ end }}{{ v }}{{ end }}
{{ for v in seq 1 5 }}{{ if v == 2 }}{{ break }}{{ end }}{{ v }}{{ end }}

Output:

12345
13579
1345
1

Whitespace Control#

Trim the expression to be expanded and the space and line feed around it.
Use {{- to trim before the tag, and -}} to trim after the tag.

{{- <statement> -}}

before {{- "text" }} after
before {{ "text" -}} after
before {{- "text" -}} after

Output:

beforetext after
before textafter
beforetextafter