Suitescript - Using a dynamically created "fieldId" in the script

I want to dynamically create a field id based upon results. I have a very basic script showing what I am trying to do. It continues to not retrieve information. I have tried using + instead of concat (''custitem' + testtext + '''). When I log the field name - it shows correctly 'custitemdoe_jane'.

You can see the script shows using the formula in two different ways. Can this be done??

 /**
 * This script looks for RTAs - updates the purchase Order and the CT record
 * 
 * @NApiVersion 2.x
 * @NScriptType ScheduledScript
 * @NModuleScope SameAccount
 */
 
define(['N/file', 'N/search', 'N/record', 'N/format', 'N/email'],
    	
function(file, search, record, format, email) {
	
	function execute(scriptContext) {
    var texty = '\'custitem';
	var testtext = 'doe_jane';
    var texty3 = '\'';
	var fieldname = texty.concat(testtext);
    var fieldname = fieldname.concat(texty3);
	
    log.debug('fieldname', fieldname);

// end result here is 'custitemdoe_jane' with the quotes

	var itemfix = record.load({
		type: record.Type.INVENTORY_ITEM, 
		id: 488, 
        isDynamic: false
		});
		   	
        var values = itemfix.getText({fieldId: fieldname});   
        var values2 = itemfix.getValue({fieldId: fieldname});    
        log.debug('values', values);
        log.debug('values', values2);

       var values3 = itemfix.getText({fieldId: fieldname.concat(texty3)});   
        var values4 = itemfix.getValue({fieldId: fieldname.concat(texty3)});    
        log.debug('values', values3);
        log.debug('values', values4);

// all of these above are blank

		itemfix.save({
			enableSourcing: true
		});    			
	   	}
		
return {execute: execute};
	
});

Your main problem, is that a field may not have quotes in its name. So you need to have custitemdoe_jane instead of 'custitemdoe_jane'.

Provided you know, what you are doing (I have failed to get the purpose of your code), to generate fieldname based on a value changed in the var testtext you need at least:

instead of:

var texty = '\'custitem';
var testtext = 'doe_jane';
var texty3 = '\'';
var fieldname = texty.concat(testtext);
var fieldname = fieldname.concat(texty3);

have this (these are minimal modifications, for clarity):

var texty = 'custitem';
var testtext = 'doe_jane';
var fieldname = texty + testtext;

this way you'll have 'custitemdoe_jane' as a field name, which is at least a valid name.

or you can use template Literals which is a modern approach by switching Apiversion to 2.1 and do it like this.

const prefix = 'custitem_'

let fieldId = `${prefix}${itemfix.getText({fieldId: fieldname});}`

In any case i would check if this for instance itemfix.getText({fieldId: fieldname}) returns a value before i create a fieldId based on it.