SpreadJS Get Context In Custom Function

<!DOCTYPE html>
<html>

  <head>
    <script data-require="jquery@*" data-semver="2.1.1" src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
    <link data-require="SpreadJS@*" data-semver="3.20142.13" rel="stylesheet" href="http://cdn.wijmo.com/spreadjs/jquery.wijmo.wijspread.3.20142.13.css" />
    <script data-require="SpreadJS@*" data-semver="3.20142.13" src="http://cdn.wijmo.com/spreadjs/jquery.wijmo.wijspread.all.3.20142.13.js"></script>
    <script src="script.js"></script>
    <link rel="stylesheet" href="style.css" />
  </head>

  <body>
    <h1>Hello SpreadJS!</h1>
    <div id="ss" style="width: 600px; height: 500px; border: 1px solid gray"></div>
  </body>

</html>

// Initialize SpreadJS
$(document).ready(function() {
    function POSITIONFunction() {
    this.name = "POSITION";
    this.maxArgs = 0;
    this.minArgs = 0;
  }
  POSITIONFunction.prototype = new $.wijmo.wijspread.Calc.Functions.Function();
  POSITIONFunction.prototype.evaluate = function(args, context) {
    return context.row + "," + context.column;
  };
  POSITIONFunction.prototype.isContextSensitive = function(){return true;};
  
  $("#ss").wijspread({
    sheetCount: 1
  }); // create wijspread control
  var spread = $("#ss").wijspread("spread"); // get instance of wijspread control
  var sheet = spread.getActiveSheet(); // get active worksheet of the wijspread control
  // initializing the active worksheet here...

  sheet.addCustomFunction(new POSITIONFunction());
  sheet.setFormula(1,1,"POSITION()");
});

/* Styles go here */

Return true in isContextSensitive method of the custom function will get a context objec as the second parameter of evaluate method of Function type. 
Context object contains some information about row/column position, sheet source...