{
    "docs": [
        {
            "_id": "123",
            "_rev": "1-7836",
            },
        {
            "_id": "456",
            "_rev": "1-1192",
           }
         ]

}

{
    "docs": [
        {
            "_id": "123",
            "_rev": "1-7836",
            "_deleted" :true
            },
        {
            "_id": "456",
            "_rev": "1-1192",
            "_deleted" :true
           }
         ]

}

function main(params) {
for (var i = 0; i< params.docs.length; i++) {
for (var value in params.docs[i]) {
if(value == '_rev'  && params.docs[i]._rev ){
var string1 = JSON.stringify(params.docs[i]);
var str = ',';
var string2 = '"';
var string3 =str+string2+ '_deleted'+ string2+ ':' + "true" ;
var res =  string1 + string3  ;
}
}
}
}
  ######################
[
  "2018-01-23T09:44:23.568738362Z stdout:
  {"_id":"123",
  "_rev":"1-7836"},
  "_deleted":true"]