Variables

Output a value

Wrap a variable name in double braces. Whitespace inside the braces is optional.

1# {{ title }}23By {{author}}

Filters can transform a value before it is written. They run from left to right.

1{{ title | trim | title }}2{{ tags | join:", " }}

Value types

Knap accepts unknown application values rather than imposing a schema. Templates commonly work with strings, numbers, booleans, arrays, objects, and nullish values.

Access nested values

Use dot notation for nested object properties and bracket notation for array items or keys that are easier to express as strings.

1{{ author.name }}2{{ authors[0].name }}3{{ metadata["article:section"] }}

Bracket expressions can also use another variable, which is useful when two arrays need to be read in parallel.

1{% for line in transcript %}2{{ timestamps[loop.index0] }} — {{ line }}3{% endfor %}

Use human-readable names

Variable output supports names with spaces, so imported column headings can remain readable without preprocessing.

1{{ First name | trim }}2{{ Publication date | date:"YYYY-MM-DD" }}

Resolve values asynchronously

If a value is not present in the variables object, the host can load it with resolveVariable. Local values always take precedence.

1const result = await engine.render('{{ remoteValue | upper }}', {2  variables: {},3  context: { documentId: 'example' },4  resolveVariable: async (name, { context }) => {5    if (name === 'remoteValue') {6      return loadValue(context.documentId);7    }8    return undefined;9  },10});

Assign a local variable

Use {% set %} to name a literal, expression, or filtered value for the rest of the template.

1{% set slug = title | lower | replace:" ":"-" %}2File: {{ slug }}.md

Assignments are evaluated in order and can be used by later output, conditions, and loops.