Analyze variable usages in Hogan.js templates

Usage no npm install needed!

<script type="module">
  import hoganVar from 'https://cdn.skypack.dev/hogan-var';



Analyzes variable usages in Hogan.js templates. Useful for static analysis, documentation generation, and sample rendering of arbitrary templates.


npm install hogan-var


const hogan = require('hogan.js');
const scanVariables = require('hogan-var').default;

const text = `Welcome to {{{placeHtml}}}!
  Greetings to:
  - {{.}} {{>icon}}
const tree = hogan.parse(hogan.scan(text), text);
const vars = scanVariables(tree);

The code above outputs the following:

  "placeHtml": {
    "scalar": true,
    "unescaped": true
  "names": {
    "array": true,
    "members": {
      "length": {
        "scalar": true,
        "section": true,
        "noninverted": true
    "section": true,
    "noninverted": true,
    "elements": {
      "scalar": true,
      "escaped": true
  "icon": {
    "partial": true

API Reference

scanVariables(tokens, options, context, parentContexts) ⇒

Walks an array or tree of Hogan.js tokens (returned by scan or parse, respectively) and returns a mapping of variable references to objects describing the contexts in which they are used. Using a parsed token tree is recommended for obtaining the most accurate interpretation.

Each variable maps to an object that may contain the following properties:

  • name (string): The name of the variable, if includeName is true in the options
  • scalar (boolean): The variable was used in a scalar context: {{v}}, {{{v}}}, {{&v}}
  • escaped (boolean): The variable was used in an escaped reference: {{v}}
  • unescaped (boolean): The variable was used in an unescaped reference: {{{v}}}, {{&v}}
  • section (boolean): The variable was used in a section: {{#v}}, {{^v}}
  • noninverted (boolean): The variable was used in a normal/non-inverted section: {{#v}}
  • inverted (boolean): The variable was used in an inverted section: {{^v}}
  • partial (boolean): The variable/filename was used in a partial: {{>v}} (top-level context only)
  • array (boolean): The variable was used as an array in a section (containing {{.}})
  • members (Object): An object mapping member variable references to usage context
  • nested (Object): An object mapping nested variable references to usage context

The difference between members and nested is that members are known to be members of the containing variable, generally because they were referenced using dot-notation. Nested references may be references to members of the containing variable or references to members of any containing scope, including the top-level scope.

The following options can be used to control interpretation:

  • arrayLengthMember (string): name of member reference assumed to be an array length, default length
  • collapseNested (boolean): whether to assume section references with same name as an outer variable refer to the same variable, default true
  • includeName (boolean): whether to (redundantly) include the name of the variable in its property map, default false

Kind: global function
Returns: the populated context argument

Param Type Description
tokens Array an array or tree of Hogan.js tokens
options Object options controlling interpretation
context Object receives variables for the current scope, defaults to an empty object
parentContexts Array an array of containing scopes, starting with the root


hogan-var is available under the ISC license.