{{ $dateFormat := .Site.Params.dateFormat | default ":date_medium" }}
{{- $.Scratch.Add "index" slice -}}
{{- range (where .Site.RegularPages "Type" "in" .Site.Params.mainSections) -}}

    {{- $.Scratch.Add "index" (dict "title" .Title
                               "tags" .Params.tags
                               "categories" .Params.categories
                               "contents" (.Summary | plainify)
                               "date"  (time.Format $dateFormat .Date)
                               "permalink" .Permalink) -}}
{{- end -}}
{{- $.Scratch.Get "index" | jsonify -}}