Loading of script tag is slower in Chrome than Firefox

I want to load large amounts of data from a local file in an html application.

At the moment my strategy is to keep the data as javascript arrays in separate .js files and load them by dynamically adding elements to the header of the page, like so:

const head = document.getElementsByTagName['head'][0]
const js = document.createElement('script')
js.async = true
js.src = "localDataFile.js"
head.appendChild(js)

The contents of localDataFile.js look like the following, where dataString contains the data encoded as a base64 string.

const base64DataString = "..."
globalFunction(base64DataString)

An example .js file I am using has a size of 300 MiB.
This file takes ~40 seconds to load in Chrome v112, and ~17 seconds in Firefox v102.

My question:
Is there any way to speed up parsing of this javascript file for Chrome, or both?
More generally, are there any better strategies in getting the data to the html application without using a web server?