if/else defines plus or minus in function

Question

I have two practically identical functions. The only difference between them are one has + and one has -. These are used about 20 times in each function, so I'd love to make this simpler with a var.

I'm still very new to JavaScript, so I don't know where to start, but something like:

if ( blah blah ){
    var symbol = '-';
} else{
    var symbol = '+';
}

var example = value1 [symbol] value2;

Thanks

Answer 1

Use this:

var modifier = (blah blah) ? 1 : -1;
var example = value1 + (modifier * value2);