Multiplying arrays, passing them through function args

So, I've ran into a nother problem. I've been playing with this loop for awhile now, and I cant get it produce anything more than 9 0's. (Which is weird cause it doesn't mess with battlers.)

Code:

    switch (diffSetting) {
      case 0:
        var total = 0;
        for (var i = 0; i < this.enemy().params[paramId].length; i++) {
          total = this.enemy().params[i] * easyParam[i];

        }
        console.log(total);
        return this.enemy().params[total];
      break;

I'm thinking I either am setting up the loop wrong, or I'm using the wrong array.

EDIT:
Well I thought I found an easier way to do this (less code), but I keep getting an "unexpected '=>'" found. I'm not sure if this engine doesn;t support it, or I'm using it wrong (most likely case)

Code:

        var enp = this.enemy().params[paramId];
        var esp = easyParam;
        var total = enp.map((a, i) => a + esp[i]).reduce((t, n) => t * n);
        console.log(this.enemy().params[total])
        return this.enemy().params[total];

EDIT2:

I am an absolute idiot. Like really. I tried to make this more complicated then it really is LOL.

Code:

        var easyDifficulty = Math.floor(this.enemy().params[paramId] * easyParam[paramId]);
        return easyDifficulty;

Man oh man...