Hi Chen,

     Here is the corrected code for your requirement, Here you need to pass the object and attribute name in the action get the value for attribute

// This file was generated by Mendix Studio Pro.

//// WARNING: Only the following code will be retained when actions are regenerated:

// - the import list

// - the code between BEGIN USER CODE and END USER CODE

// - the code between BEGIN EXTRA CODE and END EXTRA CODE

// Other code you write will be lost the next time you deploy the project.

import "mx-global";

import { Big } from "big.js";

// BEGIN EXTRA CODE// END EXTRA CODE

/** 

* @param {MxObject} projectCompletionDateObject 

* @param {string} attributeName 

* @returns {Promise.<string>} 

*/export async function GetAttributeValue(projectCompletionDateObject, attributeName)

{   

// BEGIN USER CODE   

const value = projectCompletionDateObject ? projectCompletionDateObject.get(attributeName) : undefined;   

return value;   

// END USER CODE

}