Freemarker function that generates a URL friendly "slug" from a given string

strSlug.ftl

<#-- The strSlug function generates a URL friendly "slug" from the given string -->
<#-- TODO: convert non-ASCII chars to ASCII chars -->
<#-- Copyright (c) 2018 Thomas Wilhelm <thomas.p.wilhelm@gmail.com> -->
<#function strSlug title seperator="-" idSafe=true>
  <#local flipped = "_" />
  <#if seperator == "_">
    <#local flipped = "-" />
  </#if>

  <#local string = title?replace("[" + flipped + "]+", seperator, "r") />
  <#local string = string?lower_case />
  <#local string = string?replace("[ \t\n\x0B\f\r]+", seperator, "r") />
  <#local string = string?replace("[^" + seperator + "a-z0-9]+", seperator, "r") />

  <#if idSafe == true>
    <#local string = string?replace("^" + seperator, "", "r") />
  </#if>

  <#local string = string?replace("[" + seperator + "]+", seperator, "r") />

  <#return string />
</#function>