Add addition dimension without hardcoding the fields

If the input is:

[
{"{#NAME}":"hello","age":"4"},
{"{#NAME}":"pattern","age":"8"}
]

JavaScript preprocessing is:

var data = JSON.parse(value);
var output = [];
var row;
for(var el = 0; el < data.length; el++) {
  row = data[el];
  if (data[el]['{#NAME}'] == 'pattern') {
  row['{#PATTERN}'] = 'yes';
  } else {
  row['{#PATTERN}'] = 'no';
  }
  output.push(row);
}
return JSON.stringify(output);

Then the output will be:

[
{"{#NAME}":"hello","age":"4","{#PATTERN}":"no"},
{"{#NAME}":"pattern","age":"8","{#PATTERN}":"yes"}
]