JavaScript syntax query

I'm selecting choices at a Multiple Choice (multi answer) question using JavaScript based on answers to previous Multiple Choice (multi answer) questions, so part of my js includes:
var fromQ5 = "${q://QID124/SelectedChoicesRecode}";
for (let step = 1; step < 70; step++) {
if(fromQ5.includes(step)) this.setChoiceValueByRecodeValue(step, true);
}
This works well however, if someone has selected, say, choice 56, then the js will also select choices 5 and 6 (as they 56 contains 5 and 6).
I thought I could try and embed the step var within text e.g. step + "," - but there is conflicting advice online how do that.
But also, I'm worried that won't quite solve the problem, as "56," also contains "6,".