Preserve variables set within userscript

Question

I am writing a script in tampermonkey.

I have an var arr = ["alex", "felix"] which can be updated according to the usage of script. When there is a change I added the value to the arr as; arr.push("kelix")

But when the script is reloaded, the arr is still var arr = ["alex", "felix"]. The newValue is not pushed to the array. So how can I preserve the changes in the variable arr?

What should I do?

Answer 1

I would use localStorage. Below see example script that will allow you to change document title and will remember it over reloading:

// ==UserScript==
// @name        Remember value
// @namespace   util
// @description Test that remembers any saved value after reload
// @include     http://stackoverflow.com/*
// @version     1
// @grant       none
// ==/UserScript==
// Try to load saved data from local storage
const FIELD_NAME = "userscript_TEST";
var saved = localStorage[FIELD_NAME]?JSON.parse(localStorage[FIELD_NAME]):{};

// Save data when leaving tab
window.addEventListener("unload", function() {
    localStorage[FIELD_NAME] = JSON.stringify(saved);
});
// This changed document title and remembers it
window.changeDocumentTitleForever = function(title) {
    saved["title"] = title;
    document.title = title;
}

// This loads title after loading page
if(saved.title)
    document.title = saved.title;

Usage in console:

changeDocumentTitleForever("test")