Hi bazzasherlock, that's cool!
Sure, I made the code for this game open source some time ago. You can find it on my Github repo.
In particular, have a look at the checkMatches function, line 91 of the drop7.es6 file (here). As you can see, I first iterate through the whole grid and push into a list all the discs that are supposed to explode. Then, I call explosionAnimStart (line 115) passing all the discs that should explode as an argument in one single call.
The other files contain the rest of the code, such as the specifics on the explosion animation.
Hope this helps, good luck with your game development!