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Tuesday, September 15, 2015

JavaScript: Converting CSV to Array

Google Apps Script is a scripting language based on JavaScript that lets you do new and cool things with Google Apps like Docs, Sheets, and Forms.

Although there is  jquery loaded in the javascript.html file for use in the UI. Ignoring it gives a new reasons for learning javascript as a language. Here are some functions and snippets that are good to have for data manipulation and string handling. You could probably find them by doing a search but having them here means that search will have more hits.

This function is a nice tool because when data is being imported and exported  for use in different programs CSV, comma separated values, files are the common handler.  But once you have the data then you need a program language data type. Arrays have proven to be the most useful data type in the handling of stringified information.


<script type="text/javascript">

 // This will parse a delimited string into an array of
 // arrays. The default delimiter is the comma, but this
 // can be overriden in the second argument.
 function CSVToArray( strData, strDelimiter ){
  // Check to see if the delimiter is defined. If not,
  // then default to comma.
  strDelimiter = (strDelimiter || ",");

  // Create a regular expression to parse the CSV values.
  var objPattern = new RegExp(
   (
    // Delimiters.
    "(\\" + strDelimiter + "|\\r?\\n|\\r|^)" +

    // Quoted fields.
    "(?:\"([^\"]*(?:\"\"[^\"]*)*)\"|" +

    // Standard fields.
    "([^\"\\" + strDelimiter + "\\r\\n]*))"
   ),
   "gi"
   );


  // Create an array to hold our data. Give the array
  // a default empty first row.
  var arrData = [[]];

  // Create an array to hold our individual pattern
  // matching groups.
  var arrMatches = null;


  // Keep looping over the regular expression matches
  // until we can no longer find a match.
  while (arrMatches = objPattern.exec( strData )){

   // Get the delimiter that was found.
   var strMatchedDelimiter = arrMatches[ 1 ];

   // Check to see if the given delimiter has a length
   // (is not the start of string) and if it matches
   // field delimiter. If id does not, then we know
   // that this delimiter is a row delimiter.
   if (
    strMatchedDelimiter.length &&
    (strMatchedDelimiter != strDelimiter)
    ){

    // Since we have reached a new row of data,
    // add an empty row to our data array.
    arrData.push( [] );

   }


   // Now that we have our delimiter out of the way,
   // let's check to see which kind of value we
   // captured (quoted or unquoted).
   if (arrMatches[ 2 ]){

    // We found a quoted value. When we capture
    // this value, unescape any double quotes.
    var strMatchedValue = arrMatches[ 2 ].replace(
     new RegExp( "\"\"", "g" ),
     "\""
     );

   } else {

    // We found a non-quoted value.
    var strMatchedValue = arrMatches[ 3 ];

   }


   // Now that we have our value string, let's add
   // it to the data array.
   arrData[ arrData.length - 1 ].push( strMatchedValue );
  }

  // Return the parsed data.
  return( arrData );
 }

</script>

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