A content script can survive for the same time that a webpage remains in the tab (i.e. not through refresh, or navigating to a new page). You can not make this longer. A background script can exist for the time that Chrome is running from starting Chrome through exiting. If you want to save settings, you can use chrome.storage, or store the setting in the background page. You can then read the settings, or get them from the background page, when your content script starts again when the page is refreshed, or the user navigates to a new page. Using chrome.storage will allow you to persist the option until turned off. Using chrome.storage, even if Chrome is exited and restarted later, the option information will still be available. If you just store the data in a variable in the background page, it will not persist through exiting and restarting Chrome.
If you are changing a setting in a content script it will live only as long as the content script unless you get the information somewhere will it will persist longer. That means chrome.storage or messaging the information to a background script. Either way, if you want to have the setting active when the content script next runs (refresh, navigating) you will have to get the setting back (e.g. reading from chrome.storage or receiving a message from a background script).
In general, changing options in the content script is, probably, not a good idea. It is uncommon for such to be done in the content script. On the other hand, depending on what you are doing, changing some of your extension's options in a content script may be the most appropriate.
How best to organize this depends on what you are doing. To go further really requires more information from you (e.g. code that shows what you are doing). There are many examples around of having settings persist, although usually not changed from a content script. Settings are mostly changed from options pages, popups, etc.
If your function is as simple as "ticking the enable box and having the background changed to the option selected", having the selection take place in the content script is not a good idea. In that case, you should have a browser_action button which is either a toggle, or that brings up a popup where a checkbox could be ticked (if you have multiple options). The background script would then inject the content script using chrome.tabs.executeScript() only when the feature was enabled.
Update:
Based on the new information you have added to your question, it sounds like you should use a popup which will allow you to have multiple options, or a list of sites on which your add-on is enabled. If you are looking for an example, you can take a look at the Chrome developer options page example. You can have that as a popup with a `browser_action button in addition to being an options page by adding the following to your manifest.json
"browser_action": {
"default_icon": {
"48": "myIcon.png"
},
"default_title": "Show panel",
"default_popup": "options.html"
},
If interested, my answer to this question shows using a single page as both an options page and popup. It shows how to get the data from the options page into chrome.storage and read it back. It is a bit more complicated than potentially desired as it shows four slightly different methods of communicating the information from the popup to a background page. It is tested and working in both Chrome and Firefox.
Here is an example of reading data (useDirect and emailAddress) from chrome.storage and placing the information in the DOM (to show the current value on an options page/popup):
// Restores select box and input using the preferences
// stored in chrome.storage.
function useStoredOptionsForDisplayInDOM() {
chrome.storage.local.get({
useDirect: 0,
emailAddress: '',
enabled: false
}, function(items) {
//Store retrieved options as the selected values in the DOM
document.getElementById('useDirect').value = items.useDirect;
document.getElementById('email').value = items.emailAddress;
document.getElementById('enabled').checked = items.enabled;
});
}
This is how those same values are stored in chrome.storage:
function saveOptions() {
let useDirectValue = document.getElementById('useDirect').value;
useDirectValue = +useDirectValue; //Force to number, not a string
let email = document.getElementById('email').value;
let functionEnabled = document.getElementById('enabled').checked;
chrome.storage.local.set({
useDirect: useDirectValue,
emailAddress: email,
enabled: functionEnabled
});
}
And the <body> of the HTML:
<body>
<div id="optionsArea">
Use direct method:
<select id="useDirect">
<option value="0">Option 0</option>
<option value="1">Option 1</option>
<option value="2">Option 2</option>
<option value="3">option 3</option>
</select>
<div>Email:
<input id="email"></input>
</div>
<label>
<input type="checkbox" id="enabled">
Enable functionality.
</label>
</div>
<script src="options.js"></script>
</body>
