Updating a result in JSON with a dynamic variable name
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I need to update a value in my JSON. 

My JSON result looks like this:

    results = {"ROWCOUNT":50,"COLUMNS":["PERSONID","NAME"],"DATA":{"PERSONID":["42","43","44"], "NAME":["JOE","TOM","JANE"]}
    resultData = results.DATA

In the below code I am looping over the result set and attempting to update a value at a position. I believe it is failing because I am not using dynamic variables correctly.

    var columnName = "NAME";

    for(i=0; i < results.ROWCOUNT; i++ ){
     resultData.columnName[i] = "foo" // failing here due to "columnName" being dynamic.
    }
