How can we have multiple mail IDs' in the mail snippet of the XSJS

I was building an application which included the mail notification to multiple people and the user of the session. I have tried by including the mail id with comma separation, assigning multiple emails to the single variable and using a variable in "to " section. I am getting unidentified notation in the to section.With single mail id, code is working perfecty fine.

snippet :

usermail = "testmail@sap.com " + "test1@sap.com"

var mail = new $.net.Mail({

sender: {address: "abc@sap.com"},

to: [{ address : usermail }],

subject: "Test Details",

parts: [ new $.net.Mail.Part({

type: $.net.Mail.Part.TYPE_TEXT,

text: output,

contentType: "text/plain"

})]

Thanks in advance