Random math in API?

I am trying to create an API script that will give a random result (which I have gotten to work) and within the posted result have the script also randomly generate a number. For instance: {low:  7, high:  8, result: "Extra Damage", effect: "You have taken a serious hit, As a result you suffer an additional XXXX hp of damage. "}, With XXXX being the randomly generated number.  I know roll 20 has the  Math.random() function but i cannot seem to figure out where to insert it.

In roll20 there is also the randomInteger() function. For inserting, you can do this {low:  7, high:  8, result: "Extra Damage", effect: `You have taken a serious hit, As a result you suffer an additional ${randomInteger(6)+6} hp of damage. `}, randomInteger(6)+6 is the equivalent of 1d6+6. Notice the style of quotes are backticks, not single or double quotes, found at the top left of most keyboards. If you have a string with backticks, you can put ${ } in it, and then inside the curly brackets you can put any valid javascript code.