Bold, Underline and format text in javascript

Good morning all , I have the below script and would like to know how , if at all possible, if i can underline and bold some of the information in the JS below as well as formatting the phone numbers to read "(123) 456-7890" or similar . As of right now the phone number are reading" 1234567890"

Currently the scrupt is triggered via a button commant 

JS:

(I have bolded and underlined what i am trying to accomplish in the script)

Thank you for any help or guadance you are able to provide. 

//

var w1 = this.getField("DD_Writer").valueAsString;
var w2 = this.getField("Calc_WriterPosition").valueAsString;
var w3 = this.getField("Calc_WriterPhoneNumber").valueAsString;
var w4 = this.getField("Calc_WriterEmail").valueAsString;
var s1 = this.getField("DD_Secondary").valueAsString;
var s2 = this.getField("Calc_SecondaryPosition").valueAsString;
var s3 = this.getField("Calc_SecondaryPhoneNumber").valueAsString;
var s4 = this.getField("Calc_SecondaryEmail").valueAsString;
var m1 = this.getField("Date_LetterDate").valueAsString;
var m2 = this.getField("DD_SMQuarter").valueAsString;
var m3 = this.getField("DD_SMYear").valueAsString;
var m4 = this.getField("Date_DocDueDate").valueAsString;
var r = this.getField("Calc_Text");

r.value = "\n" + m1 + "\n\n\nDear,  Participant" +

"\n\nI hope this letter finds you well." +

"\n\nEach quarter NA is required to collect receipts from each participant for services you have received outside of NA. This includes billing statements from service providers such as doctors, dentists, and hospitals. From insurance companies it is called an “explanation of benefits”. If you have an in home care giver or COPES worker, we need a current award letter." +

"\n\nPlease reach out to any service providers you have utilized in the months of " + m2 + " " + m3 + " and request receiptsfor the services you used." +

"\n\nI have included a letter for you to show your provider in an effort to collect the documentation we need." +

"\n\nDue to privacy laws, NA cannot request this information directly from the provider. However, we want to support your effort as much as possible" +

"\n\nAll documentation is due to " + s1 + " ,or myself by " + m4 + "." +

"\n\nIf you need any assastance or have questions about what services qualify please reach out to us. " + s1 + " can be eached at " + s4 + " or by phone at " + s3 + "." + "I can be reached at " + w4 + " or by phone at " + w3 + "." +

"\n\nBy meeting our service match obligation, we can ensure funding for our housing voucher. We can do this together!" +

"\n\nIn Gratitude," +

"\n\n\n\n" + w1 + "\n" + w2 + "\nNA" + "\nCell: " + w3;

//

Please let m eknow if you would like a copy of my file and i can try and send it.