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+---
+title: collections.IsSet
+linkTitle: isset
+description: Reports whether the key exists within the collection.
+categories: [functions]
+keywords: []
+menu:
+  docs:
+    parent: functions
+function:
+  aliases: [isset]
+  returnType: bool
+  signatures: [collections.IsSet COLLECTION KEY]
+relatedFunctions:
+  - collections.Dictionary
+  - collections.Group
+  - collections.Index
+  - collections.IsSet
+  - collections.Where
+aliases: [/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`:
+
+```go-html-template
+{{ 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:
+
+```go-html-template
+{{ 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 %}}