How do I make a javascript regex or generation code

[63]

Hey people, I have some code for amazon.com and its supposed to generate multiple codes with a certain regex. Does anyone know how i can change this code to a regex like this :

Code:

[A-Z1-9]{4}-[A-Z1-9]{6}-[A-Z1-9]{5}

that would produce a code like this: R26X-NT5XPT-TZ6A1 but random.
Here is my javascript code. BTW, i didn't make this.

Code:

 
var speed = prompt("Enter a speed")

function makeid() {

var text = "";

var possible = "6SJXEoQ0Htx4WhvKgu2b3fIrle8wBZs1MRpT9PGyDCLVUmYO5AdiankFc7qjzN"; //This is what needs to be changed

for (var i = 0; i < 14; i++)

text += possible.charAt(Math.floor(Math.random() * possible.length));
return text;

}
function main() {

//whatever
}
setInterval(function() {

main();

}, speed);

I am a COMPLETE javascript noob, so i have no idea what im doing. I'm only good at regular java. Thanks to anyone who can help!