Helper functions

In order to facilitate the writing and use of converters, a number of handlebars helper functions are available in the context of TEv2, that extend the built-in helper functions of Handlebars.

Helper functions would typically use variables as specified in the converter profile for the TEv2 tool that they are used in.

Helper functions can be used within handlebars expressions. Their input is the evaluated value of the expression that follows the call, possibly with extra options.

helper function syntax format

{{<helperfunction> <element> <argument>="<value>"}}
{{capFirst entry.term}}
{{noRefs entry.glossaryText type="markdown"}}

List of built-in helpers

Here is a summary of the handlebar helpers that can always be used; you can click on the helper to navigate to a more detailed description of how they work (with examples):

Helper	Functional summary
#if	conditionally render a text block.
#unless	this is the inverse of #if.
#each	Iterates over a list of elements. Inside the block, you can use this to reference the element being iterated over.
#with	Enables you to change the evaluation context of template-parts.
lookup	Allows for dynamic parameter resolution using Handlebars variables.

capFirst

The function of the helper capFirst is to capitalize every first character from every word in a string.

Examples for 'capFirst'

{{capFirst entry.glossaryTerm}}   // e.g. "converter profile" becomes "Converter Profile"
{{capFirst entry.glossaryText}}   // e.g. "This is a description; for SOME TERM" becomes "This Is A Description; For SOME TERM"

The helper capFirst replaces the first character of every word of its argument with the capitalized equivalent. Words are obtained by splitting the input on space characters.
It takes a string as input, splits the string at spaces, capitalizes the first character of every split item, reconstructs the input string fomr the split items, and returns the result.

log

The function of the helper log is to output a text string to the log of a tool that uses a converter from which it is called. This allows users to enhance debugging output.

This helper extends the [functionality of the log helper that is built into [Handlebars itself]https://handlebarsjs.com/guide/builtin-helpers.html#log). The helper is based on tslog, which has lots of other features.

Particular to our log helper is the feature that allows users to suppress log messages. This is useful, for example, when using a converter in the HRGT that determines whether or not to allow an MRG entry to appear in the HRG that is being created. In such cases, the log would be littered with log messages that no output is being generated, which can now be suppressed.

This feature is implemented through the log level silent. Other log level values are provided by tslog. When a log level isn't specified, it defaults to warn.

Examples for 'log'

// The following logs a warning of the form '<path>/<file>@<line>:pos', which specifies where an error occurred.
{{log '<errmsg>:' err.dir '/' err.file '@' err.line ':' err.pos level='warn'}}"

// The following logs the text 'This is an informational message'
{{log level='info' 'This is an informational message'}}

// Examples below will prevent errors caused by the conversion call from being logged
{{log level='silent' 'This message will not be logged'}}
{{regularize entry.term}}{{log level='silent'}}

noRefs

The function of the helper noRefs is to replace all TermRefs from a string, with its (capitalized) showtext. Capitalization is done by the helper capFirst.

danger

The usefulness of the noRefs helper has its limits. For example, in a context that allows two or more (customized) syntaxes for TermRefs, the noRefs helper can miss one or more of these (custom) syntaxes, producing a result that will not be rendered as expected by the static site generator. One way to deal with such situations is to identify where it may occur, and try to provide input to the noRefs helper that does not contain (such) TermRefs. In the concrete situation of popups, for which typically glossaryText fields are used that might produce such erroneous renderings, a workaround would be to add a popupText field (or so) whose value is manually constructed from the glossaryText, and is void of (such) TermRefs.

The following tabs show how this helper works on the following input:

---

  [Markdown](link), <a href="link">HTML</a>, `[showtext](someterm@somescope)`

(No type specified)

Calling {{noRefs entry.glossaryText}} results in:

  [Markdown](link), <a href="link">HTML</a>, Showtext

type="markdown"

Calling {{noRefs entry.glossaryText type="markdown"}} results in:

  Markdown, <a href="link">HTML</a>, Showtext

type="markdown, html, interpreter"

Calling {{noRefs entry.glossaryText type="markdown, html, interpreter"}} results in:

  Markdown, HTML, Showtext

Note that the TermRef is also seen as a markdown link, and hence remo

type="/[(?<showtext>[^]]+)]((?:[^)]+))/, html"

Calling {{noRefs entry.glossaryText type="/\[(?<showtext>[^\]]+)\]\((?:[^)]+)\)/, html"}} results in:

  Markdown, HTML, Showtext

---

The helper noRefs uses the configured type to convert all references to the showtext property of the interpreted reference. It also capitalizes the showtext replacement using the capFirst helper.
It takes the input, finds matches using the configured syntax-type, and uses the capitalized interpreted showtext property as a replacement, after which the output is returned.

Three standard values are available to be used as the value for the type option. Multiple values may be provided, in which case the values are interpreted in order from left to right. If no value is provided, 'interpreter' is used as the default type. If a type is provided that does not match any of the standard type values, the value is assumed to be a custom regex.

Available type values:

type	Description
interpreter	Uses the regex of the configured interpreter to find matches.
html	Uses the regex <a\b[^>]*?>(?<showtext>.*?)<\/a> to find HTML <a> tags and uses the value in between the opening and closing tag as showtext.
markdown	Uses the regex \[(?<showtext>[^\]]+)\]\((?:[^)]+)\) to find Markdown hyperlinks and uses the link text as showtext.
custom	A value for type that does not match any of the standard type values is assumed to be a custom regex.

regularize

The function of the helper regularize is convert human readable text into a regularized text, which is a common text format within TEv2 (particularly in MRG entries) for automated processing.

Examples for 'Regularize'

// Input (entry.term): "EX(ample)"
{{regularize entry.term}}
// Output: "ex-ample"

The helper regularize converts the input string into a regularized text, according to the regularization process.

localize

The function of the helper localize is to convert an absolute URL to a relative path within a particular website context, enhancing internal navigation efficiency and consistency.

The website context is specified by the website value of the MRG in the converter profile.

`website` = `https://github.com/tno-terminology-design/tev2-specifications/tree/master`

Examples for 'localize'

// Input (entry.navurl): "https://github.com/tno-terminology-design/tev2-specifications/tree/master/docs/specs/syntax/handlebars-helper-functions"
{{regularize entry.navurl}}
// Output: "/docs/specs/syntax/handlebars-helper-functions"

`website` is something else

Examples for 'localize'

// Input (entry.navurl): "https://github.com/tno-terminology-design/tev2-specifications/tree/master/docs/specs/syntax/handlebars-helper-functions"
{{regularize entry.navurl}}
// Output: "https://github.com/tno-terminology-design/tev2-specifications/tree/master/docs/specs/syntax/handlebars-helper-functions"

The helper localize parses the value it was given as a URL and compares it to the website value of the MRG in the converter profile. If both the host values (e.g., tno-terminology-design.github.io) match, the pathname of the URL is returned. If the given value cannot be interpreted as a URL, or the host values do not match, the input value is returned. This can be useful in situations where external links (URL's pointing to a website other than the current host) are handled differently from internal links.

ifValue

The ifValue helper allows you to conditionally display text based on various comparisons. This can be useful for showing or hiding content depending on specific values, statuses, or other conditions.

equals

equals

The equals option checks if a value is strictly equal to a specified value. This is useful when you want to display content only if a field matches exactly with the expected value.

Example: Display a Warning for Deprecated Terms

If the status of a term is "deprecated," show a warning message.

Example Usage of 'equals'

{{#ifValue entry.status equals="deprecated"}}
**Warning**: this term is deprecated!
{{/ifValue}}

• What This Does: If entry.status is "deprecated", the warning text is displayed.

notEqual

notEqual

The notEqual option checks if a value is not equal to the specified value. This is useful for excluding content based on certain conditions.

Example: Exclude Active Terms

If a term's status is not "active," display a note.

Example Usage of 'notEqual'

{{#ifValue entry.status notEqual="active"}}
Note: This term is not currently active.
{{/ifValue}}

• What This Does: If entry.status is anything other than "active", the note is displayed.

greaterThan

greaterThan

The greaterThan option checks if a numeric value is greater than a specified number. This is useful for comparisons like age, quantity, etc.

Example: Age Check for Adults

Show a message if the age is greater than 18.

Example Usage of 'greaterThan'

{{#ifValue entry.age greaterThan=18}}
You are an adult.
{{/ifValue}}

• What This Does: If entry.age is greater than 18, the message "You are an adult." is displayed.

greaterThanOrEqual

greaterThanOrEqual

The greaterThanOrEqual option checks if a numeric value is greater than or equal to a specified number.

Example: Age Check for Voting Eligibility

Show a message if the age is 18 or older.

Example Usage of 'greaterThanOrEqual'

{{#ifValue entry.age greaterThanOrEqual=18}}
You are eligible to vote.
{{/ifValue}}

• What This Does: If entry.age is 18 or more, the message "You are eligible to vote." is displayed.

lessThan

lessThan

The lessThan option checks if a numeric value is less than a specified number.

Example: Age Check for Minors

Show a message if the age is less than 18.

Example Usage of 'lessThan'

{{#ifValue entry.age lessThan=18}}
You are a minor.
{{/ifValue}}

• What This Does: If entry.age is less than 18, the message "You are a minor." is displayed.

lessThanOrEqual

lessThanOrEqual

The lessThanOrEqual option checks if a numeric value is less than or equal to a specified number.

Example: Age Check for Underage

Show a message if the age is 18 or less.

Example Usage of 'lessThanOrEqual'

{{#ifValue entry.age lessThanOrEqual=18}}
You are underage.
{{/ifValue}}

• What This Does: If entry.age is 18 or less, the message "You are underage." is displayed.

isNull

isNull

The isNull option checks if a value is null or undefined.

Example: Check if a Value is Null

Show a message if a term's description is missing.

Example Usage of 'isNull'

{{#ifValue entry.description isNull=true}}
No description available.
{{/ifValue}}

• What This Does: If entry.description is null or undefined, the message "No description available." is displayed.

isTruthy

isTruthy

The isTruthy option checks if a value is "truthy" (non-zero, non-null, non-empty string, etc.).

Example: Check if a Feature is Enabled

Show a message if a feature is enabled.

Example Usage of 'isTruthy'

{{#ifValue entry.isEnabled isTruthy=true}}
The feature is enabled.
{{/ifValue}}

• What This Does: If entry.isEnabled is "truthy", the message "The feature is enabled." is displayed.

isFalsy

isFalsy

The isFalsy option checks if a value is "falsy" (0, null, undefined, "", false, etc.).

Example: Check if a Feature is Disabled

Show a message if a feature is disabled.

Example Usage of 'isFalsy'

{{#ifValue entry.isEnabled isFalsy=true}}
The feature is disabled.
{{/ifValue}}

• What This Does: If entry.isEnabled is "falsy", the message "The feature is disabled." is displayed.