How to sort by a string date in ElasticSearch using ElasticSearch.js

Question

I have a mapping with a field type of "text" that contains a date:

My mapping looks like this:

 "title" : "Nebula",
 "has_store" : true,
 "createdAt" : "Wed Nov 25 2020 05:37:08 GMT+0000 (Coordinated Universal Time)",

How can I sort by this date createdAt to get the newest items first?

My query is using ElasticSearch.js

     bool: {
                must: [{
                    multi_match: {
                        query: data.searchTerm,
                        fields: [
                            "data.title^2.5",
                        ],
                        operator: "or",
                        lenient: "true",
                        type: 'best_fields',
                        fuzziness: "AUTO"
                    }
                }],

            }
        },
        from: Number(data.lastKey),
        size: Number(data.size)
    }

Is there a way to use scripts to do this? If so - how can I process the date into a real date object?

Or is there a way to sort by dates using the string format I have currently?

Answer 1

It'd be best to reindex your fields as dates but if you have to sort by dates which are inside text , here's how you do it:

GET your_index/_search
{
  "sort": [
    {
      "_script": {
        "type": "number",
        "script": {
          "lang": "painless",
          "source": """
            def df = new SimpleDateFormat("EEE MMM dd yyyy HH:mm:ss 'GMT'Z '('zzzz')'");
            return df.parse(doc['createdAt.keyword'].value).getTime();
          """
          
        },
        "order": "desc"
      }
    }
  ]
}