Javascript: http request, how to iterate JSON object response

I am querying a graphQL endpoint through http request and I am getting a successful response with the data that I need to collect, however, I can’t seem to navigate through the data to pull the fields I require.

const query = JSON.stringify({query:
           '{' +
           '   all_insight_article('+
           '     locale: "en-gb"'+
           '     where: {business_unit: {business_unit: {title: "xxx"}, MATCH: ALL}, audience: {MATCH: ALL, audiences: {title: "xxx"}}publish_date_gt: "2023-02-01"}'+
           '   ) {'+
           '     items {'+
           '     audienceConnection {'+
           '         edges {'+
           '           node {'+
           '             ... on Audiences {'+
           '               title'+
           '               system {'+
           '                 uid'+
           '               }'+
           '             }'+
           '           }'+
           '         }'+
           '       }'+
           '       system {'+
           '         uid'+
           '         publish_details {'+
           '           time'+
           '         }'+
           '         updated_at'+
           '       }'+
           '       absolute_url'+
           '       title'+
           '       subtitle'+
           '       main_image'+
           '       topicsConnection {'+
           '         edges {'+
           '           node {'+
           '             ... on Topics {'+
           '               title'+
           '               display_name'+
           '               system {'+
           '                 uid'+
           '               }'+
           '             }'+
           '           }'+
           '         }'+
           '       }'+
           '     },'+
           '     total'+
           '   }'+
           ' }'
    });

var req = new HttpClientRequest("https://eu-graphql.contentstack.com/stacks/bltcxxx?environment=xxx&access_token=xxx")
req.header["Content-Type"] = "application/json"
req.method = "POST"
req.body = query
req.execute()
var response = req.response;
var posts = JSON.parse(response.body);
var articleList_json = [];

var i
for ( i = 0; i < 15; i++) {
  articleList_json.push({
    "title": posts[i].title,
  });
}

logInfo(articleList_json);

Here is the evidence of my response if I log logInfo(response.body);

Here is the JSON structure https://www.codedump.xyz/json/Y_V2SI6W4xxLXX1y

The error I get is posts is undefined.