{!REQUIRESCRIPT("/soap/ajax/34.0/connection.js")}

 
    var result = sforce.connection.query(
        "SELECT Name,top_firm__r.Coverage_Channel__c " + 
        "FROM Contact " + 
        "WHERE Id = '{!Contact.Id}' " 
    );

    var records = result.getArray("records");

 
    if(records.length != 0){
        var cont = records[0].top_firm__r.Coverage_Channel__c;
window.top.location.href="someting........";
        }

public without sharing class ContactTriggerHandler {

private boolean m_isExecuting = false;
    private integer BatchSize = 0;
     public static Set <String> EmailSet = null;
    public ET_ContactTriggerHandler (boolean isExecuting, integer size){
        m_isExecuting = isExecuting;
        BatchSize = size;
    }
    
   
    
    
    public void onInsertAndUpdate (Contact[] updatedContacts, Map<ID, Contact> OldMap) 
    {
                if(EmailSet==null){ 
                //do something
                
                    EmailSet.add(something); 
                }
    }

}

trigger ContactTrigger on Contact (after insert,  after update,before delete) {
     
    ET_ContactTriggerHandler  EThandler = new     ET_ContactTriggerHandler(Trigger.isExecuting, Trigger.size);
    
     
     public enum triggeredAction {afterInsert, afterUpdate , beforeDelete}
     
    if(Trigger.isInsert && Trigger.isAfter){
    System.debug('*******INSERT'   );
      
        EThandler.onInsertAndUpdate (Trigger.old, Trigger.new, Trigger.oldMap, triggeredAction.afterInsert) ;
    }

}

public without sharing class ET_ContactTriggerHandler {

private boolean m_isExecuting = false;
    private integer BatchSize = 0;
    public ET_ContactTriggerHandler (boolean isExecuting, integer size){
        m_isExecuting = isExecuting;
        BatchSize = size;
    }
    
    public enum triggeredAction {afterInsert, afterUpdate , beforeDelete}
    
    public void onInsertAndUpdate (Contact[] oldContacts, Contact[] updatedContacts, Map<ID, Contact> OldMap, triggeredAction ta) 
    {   

//do something

}

}

{!REQUIRESCRIPT("/soap/ajax/34.0/connection.js")}

 
    var result = sforce.connection.query(
        "SELECT Name,top_firm__r.Coverage_Channel__c " + 
        "FROM Contact " + 
        "WHERE Id = '{!Contact.Id}' " 
    );

    var records = result.getArray("records");

 
    if(records.length != 0){
        var cont = records[0].top_firm__r.Coverage_Channel__c;
window.top.location.href="someting........";
        }