hugo/docs/content/en/functions/collections/IsSet.md

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title	linkTitle	description	categories	keywords	menu	function	relatedFunctions	aliases
collections.IsSet	isset	Reports whether the key exists within the collection.	functions		docs parent functions	aliases returnType signatures isset bool collections.IsSet COLLECTION KEY	collections.Dictionary collections.Group collections.Index collections.IsSet collections.Where	/functions/isset

For example, consider this site configuration:

{{< code-toggle file=hugo copy=false >}} [params] showHeroImage = false {{< /code-toggle >}}

It the value of showHeroImage is true, we can detect that it exists using either if or with:

{{ if site.Params.showHeroImage }}
  {{ site.Params.showHeroImage }} → true
{{ end }}

{{ with site.Params.showHeroImage }}
  {{ . }} → true
{{ end }}

But if the value of showHeroImage is false, we can't use either if or with to detect its existence. In this case, you must use the isset function:

{{ if isset site.Params "showheroimage" }}
  <p>The showHeroImage parameter is set to {{ site.Params.showHeroImage }}.<p>
{{ end }}

{{% note %}} When using the isset function you must reference the key using lower case. See the previous example. {{% /note %}}