For the love of code

function advReplaceText(data, dataType, tag, docId){

  var newDoc = DocumentApp.openById(docId);

  var newBody = newDoc.getBody(); 

  var style = {};

  style[DocumentApp.Attribute.HORIZONTAL_ALIGNMENT] = DocumentApp.HorizontalAlignment.CENTER;

  var currentData = (data != undefined)?(data!=null)?data:null:null;

  while (isNullUndefined(newBody.findText(tag)) == false){   //Merges tag until no more matches found

      if (currentData == null){ //if data is a blank just clear tag.  

        newBody.replaceText(tag, "");

      }            

      else{

        switch(dataType){

          case "_Chart":

            var blob = currentData; //Extracts chart blob      

            var replacedParent = newBody.findText(tag).getElement().getParent().asParagraph(); //gets tag location

            var clearTag = newBody.replaceText(tag, ""); //removes tag                  

            var cImg = replacedParent.appendInlineImage(blob).setAttributes(style); //adds chart at tag location using set "style"

            cImg.setHeight(250).setWidth(600);        

            break;

          case "_Image":                        

            var blob = DriveApp.getFileById(currentData).getBlob(); //gets image blob from GID

            var replacedParent = newBody.findText(tag).getElement().getParent().asParagraph(); //gets tag location

            var clearTag = newBody.replaceText(tag, ""); //removes tag                  

            var cImg = replacedParent.appendInlineImage(blob).setAttributes(style); //adds image at tag location using set "style"

            cImg.setHeight(250);                  

            break;

          case "_Field":            

            newBody.replaceText(tag, currentData); //Replaces tag with value

            break;

          default:{            

            newBody.replaceText(tag, ""); //when in doubt, remove the tag. 

            break;

          }

        }        

      }    

    }    

  newDoc.saveAndClose();

};

function isNullUndefined(val){

  var result = false;

 switch (val){

   case null:

      result = true;

      break;

   case undefined:

      result =  true;

      break;

   case "":

      result = true;

      break

   default:

      result = false;

      break;      

  }    

  return result;

};