New to NetSuite | Client Script: postSourcing(scriptContext)

After discussing all the types of SuiteScript in the New to NetSuite | SuiteScript Types Overview article, we are now focusing on the different types of Client Script.  In this article, we are going to focus on one type of Client Script called postSourcing. This type of Client Script is triggered after a field is sourced—meaning its value is automatically populated by the system based on another field's value. This event is typically used to execute custom logic whenever specific field values change. 

Note: 

• Executes on transaction forms only. 

Here's a simple example of a postSourcing function:  

/** 
 * @NApiVersion 2.x 
 * @NScriptType ClientScript 
 * @NModuleScope SameAccount 
 */ 
define(['N/error','N/currentRecord'], 
function(error,currentRecord) { 
    /** 
     * Function to be executed after page is initialized. 
     * 
     * @param {Object} scriptContext 
     * @param {Record} scriptContext.currentRecord - Current form record 
     * @param {string} scriptContext.mode - The mode in which the record is being accessed (create, copy, or edit) 
     * 
     * @since 2015.2 
     */ 
    function postSourcing(scriptContext) { 
var currentRecord = scriptContext.currentRecord; 
var fieldId = scriptContext.fieldId; 
if (fieldId === 'item') { 
            // Get the value of the 'item' field 
            var itemName = currentRecord.getCurrentSublistValue({ 
                sublistId: 'item', 
                fieldId: 'item' 
            }); 
            // Set a new value for the 'description' field 
            currentRecord.setCurrentSublistValue({ 
                sublistId: 'item', 
                fieldId: 'description', 
                value: 'Description