index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    const db = {
      documents: {
        users: {
          fields: [
            {
              name: {
                type: 'string'
              },
              age: {
                type: 'number'
              }
            }
          ],
          data: [
            {
              name: 'Alex',
              age: 20
            },
            {
              name: 'Bob',
              age: 30
            },
          ]
        }
      }
    }

    const driver = {
      request(payload) {
        const document = db.documents[payload.document];
        const data = document.data.find(item => {
          if (item[payload.field.name] === payload.field.equal) {
            
            return true;
          }
        });

        return data;
      }
    }

    const data = driver.request({
      document: 'users',
      type: 'get',
      field: {
        name: 'age',
        equal: 20
      }
    });

    console.log(data);
  </script>
</body>
</html>