File Preview

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "a",
  "attributes": {
    "class": "ms-fontColor-themePrimary ms-fontColor-themeDark--hover",
    "title": "Fullscreen Preview",
    "target": "_blank",
    "href": "=if([$File_x0020_Type] == 'docx' || [$File_x0020_Type] == 'dotx' || [$File_x0020_Type] == 'dotm' || [$File_x0020_Type] == 'docm' || [$File_x0020_Type] == 'docb' || [$File_x0020_Type] == 'pptx' || [$File_x0020_Type] == 'pptm' || [$File_x0020_Type] == 'potx' || [$File_x0020_Type] == 'potm' || [$File_x0020_Type] == 'ppam' || [$File_x0020_Type] == 'ppsx' || [$File_x0020_Type] == 'ppsm' || [$File_x0020_Type] == 'sldx' || [$File_x0020_Type] == 'sldm' || [$File_x0020_Type] == 'vsdx' || [$File_x0020_Type] == 'xlsx' || [$File_x0020_Type] == 'xlsm' || [$File_x0020_Type] == 'xltx' || [$File_x0020_Type] == 'xltm', @currentWeb +'/_layouts/15/Doc.aspx?sourcedoc=' + [$UniqueId] + '&action=embedview', [$FileRef])"
  },
  "style": {
    "border": "none",
    "background-color": "transparent",
    "cursor": "pointer",
    "text-decoration": "none"
  },
  "children": [
    {
      "elmType": "span",
      "attributes": {
        "iconName": "=if([$File_x0020_Type] == 'docx' || [$File_x0020_Type] == 'dotx' || [$File_x0020_Type] == 'dotm' || [$File_x0020_Type] == 'docm' || [$File_x0020_Type] == 'docb' || [$File_x0020_Type] == 'pptx' || [$File_x0020_Type] == 'pptm' || [$File_x0020_Type] == 'potx' || [$File_x0020_Type] == 'potm' || [$File_x0020_Type] == 'ppam' || [$File_x0020_Type] == 'ppsx' || [$File_x0020_Type] == 'ppsm' || [$File_x0020_Type] == 'sldx' || [$File_x0020_Type] == 'sldm' || [$File_x0020_Type] == 'vsdx' || [$File_x0020_Type] == 'xlsx' || [$File_x0020_Type] == 'xlsm' || [$File_x0020_Type] == 'xltx' || [$File_x0020_Type] == 'xltm', 'View' , 'OpenInNewWindow')"
      }
    }
  ]
}