Generate 4 random letters, then a random number between 0-9, then four more random letters, and one more random number between 0-9 in java script

I am looking to generate a coupon code, but i need to attach a string of 4 random letters, then a random number between 0-9, then four more random letters, and one more random number between 0-9 on to a base of NONO15-....i cannot figure out what this string would be.