For those who do not wish to search for the answer:
Since the days of the ASR35 or TTYs there have been non-printable control code that included some formatting character codes like tab, new line, and carriage return. Depending upon the programing language the special code need a prefix characrter to idicate that following letter is a special code. In JavaScript that cahracter is the "\" backward slash. The new line code is "\l" and the carriage return is "\n". Some sytems or devices require both cods while others only need one. In JavaScript you can use eitehr.
this.getField("testtest").value = this.getField("address").value + "\n " + this.getField("City").value + ", " + this.getField("province").value + "\n " + this.getField("postal_code").value;