code: function (formula, element) {
        // to avoid double translate formulas, update item data in parser
        var parsed = parse(formula, element),
            value = parsed.result,
            error = parsed.error,
            nodeName = element.nodeName.toUpperCase();
  
        instance.matrix.updateElementItem(element, {value: value, error: error});
  
        if (['INPUT'].indexOf(nodeName) === -1) {
          element.innerText = value || error;
        }
  
        element.value = value || error;
  
        return parsed;
      }
docs: calculate element formula
  @param {String} formula
  @param {Element} element
  @returns {Object}