Email submit button concatenate subject and body

Hello Expert,

I'm trying to modify what the body of the email will look like once the user has pressed an email submit button. In Livecycle designer, I clicked on the button and viewed java script code

this.resolveNode("#event.#submit").target = "mailto:"+$record.XXXXXX.MAIL_ID.value+"?subject ="+" Subject line "+"&body="+"Body of the mail";

Whenever i click the button its conacatenate the subject line with -- " Subject line &body body of the mail ".

My requirement is to change the body of the mail. Can anyone help me on this issue.