filter.js

const data = {  
   "metafields":[  
      {  
         "id":5994805788772,
         "namespace":"global",
         "key":"Event-Date",
         "value":"1549256400",
         "value_type":"string",
         "description":null,
         "owner_id":15977611364,
         "created_at":"2019-02-06T18:31:44-05:00",
         "updated_at":"2019-02-06T18:31:44-05:00",
         "owner_resource":"article"
      },
      {  
         "id":5994805821540,
         "namespace":"global",
         "key":"Event-Time",
         "value":"6:00pm - 8:00pm",
         "value_type":"string",
         "description":null,
         "owner_id":15977611364,
         "created_at":"2019-02-06T18:31:45-05:00",
         "updated_at":"2019-02-06T18:31:45-05:00",
         "owner_resource":"article"
      },
      {  
         "id":6010564542564,
         "namespace":"global",
         "key":"Location",
         "value":"18th Street Location",
         "value_type":"string",
         "description":null,
         "owner_id":15977611364,
         "created_at":"2019-02-07T13:16:05-05:00",
         "updated_at":"2019-02-07T14:05:08-05:00",
         "owner_resource":"article"
      }
   ]
};

const filteredResults = data.metafields.filter(item => item.key !== "Event-Date");

console.log(filteredResults);