Thanks in advance!.<apex:page standardcontroller="Opportunity">
<apex:form id="formId">
<!-- No Opportunity fields are placed here -->
<apex:image value="/img/msg_icons/confirm16.png" style="vertical-align:top;" id="Warning_icon"/>
</apex:form>
<script>
var Original_Amount__c = '{!Opportunity.Original_Amount__c}'; //THIS DO NOT WORKS
window.onload = function()
{
var Original_Amount__c = document.getElementById({!Opportunity.Original_Amount__c}); //THIS DO NOT WORKS
//Validations with Original_Amount__c value....
};
</script>
</apex:page>
Hi Juan,You cant able to do in professional edition.You need to develop in developer edition and then deploy it to your professional org. please refer the below link.https://help.salesforce.com/s/articleView?id=000323569&type=1Thanks,Ankaiah