Issues saving and reading a variable across 2 js files

Question

So I'm trying to get a MagicMirror module to get data from ComEd's API, compare it to the previous reading, and overwrite the previous reading with the current reading. I'm trying to use import/export, but it doesn't work.

'use strict';

Module.register("MMM-ComEdPrice", {
import 'previousPrice' from "~/MagicMirror/modules/MMM-ComEdPrice/previousPrice.js";
var lastPrice = previousPrice;

    result: [],
    // Default module config.
    defaults: {
        url: 'https://hourlypricing.comed.com/api?type=currenthouraverage',
        fadeSpeed: 2000,
        updateInterval: 5 * 60 * 1000, // every 5 minutes
    },

At the beginning of the file, and

},
export { currentPrice };
});

At the end of it. The second file consists of the following:

import { currentPrice } from "modified_MMM-ComEdPrice.js";
var previousPrice=currentPrice;
export { previousPrice };

Update: Have also tried using fs, but it appears that I'm not using it correctly, as every line that I have put it throws an error.