How to define password in casual?

[smitharanga]

I need to generate a password with-
min length : 7
max length : 15
Uppercase : one letter atleast.
Lowercase : one letter atleast
Special charater : ~ ! @ # $ % ^ * ( ) _ + : ?

I used casual lib, but im unable to generate special character. Could any one help me on this issue?
var casual = require('casual');
var password = casual.password.substring(7,15);