Using Out of the box command bar javascript functions in Custom command bar buttons

Hi 

I have a requirement in Dynamics 365 8.2, just to give users an alert before sending an email. When users click on the send email button they want to see an alert are you sure you want to send this email. clicks ok (Yes) email will be sent. 

I created a custom send button and using below javascript action instead of updating out of the box button. Send email button uses send() function. I am using this function in my script below. Is this below script is fine or I have to mention the javascript library (/_static/activities/email.js) for send function explicitly? 

function EmailSendAlert()
{
//debugger;
Xrm.Utility.confirmDialog("Are you sure you want to send this Email", function(){ send(); },function(){return;});
}