How would I send multiple different values of different variables from popup.js to inject.js so those can be used in the inject.js script?

Question

Hi I am unsure on how would I send set variables from popup.js to inject.js. Lets say I've got these variables in popup.js:

// popup.js file
var year = "New Year"
var month = "New Month"
var day = "New Day"

Now I would like to send each an every single one to be used in inject.js script and I am unsure how I would do that. Any ideas?

// inject.js file
// some how import the values over from the popup.js
console.log(year + ", " + month +  ", " + day)

If anyone has any idea on how to do this please help I'am very stuck on this and I am beginner in coding so sorry if this is a question that you have seen before or its repetitive I just am looking for help thank you.

PS This is for a google extension so if any ideas could be compatible with google chrome would be grateful.

Answer 1

The old school way of doing it is to use the window and assign your variable to some properties of it. If this is a small project and you just want to get it done this is very simple.

In popup.js do,

window.myVars = {
                    "year": year,
                    "month": month,
                    "day": day
                };

Now on inject.js

console.log(window.myVars.year + ", " + window.myVars.month +  ", " + window.myVars.day)

The problem with this is you are polluting the global scope. If another javascript file ( maybe a third party library ) uses window.myVars you could run into a problem. This approach is much harder to debug and garbage collection may also be affected.

A much modern approach but would be to use the local storage API.

localStorage.setItem("year",year); // In popup.js
localStorage.getItem("yera"); // In inject.js

If you can use the latest es module feature then you could also do,

export const getYear = (() => year ); // In popup.js
export const getMonth = (() => month );
export const getDay = (() => day );

then in inject.js,

import getYear,getMonth,getDay from ./popup.js

console.log(getYear());