How to use Firefox API for extensions to find and close unwanted tabs.

Tabs in Firefox can be manipulated via browser.tabs collection. This collection is available only for extensions. So open about:debugging choose This Firefox and from the list of extensions Inspect one which has permission tabs. I chose uBlock Origin ad blocker since it needs lots of permissions, so I assumed it has tabs permission.

Saving open tabs into a variable

First we save a list of open tabs into a variable tabs:

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var tabs = []

I’m using var since let prevents redeclaration which makes copy/paste annoying. The following function saves current tabs into tabs variable:

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function refreshTabs() {
    browser.tabs.query({currentWindow: true}).then(result => {
        tabs = result
        console.info("Tabs from current window saved into variable tabs")
    })
}

We have to call it now and whenever currently open tabs change.

Close duplicate tabs

To find duplicates we will group tabs by URL:

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function groupTabsBy(tabs, f) {
    const grouped = new Map()

    for (const tab of tabs) {
        const key = f(tab)
        if (!grouped.has(key))
            grouped.set(key, [])

        grouped.get(key).push(tab)
    }

    return grouped
}

After the tabs are grouped in a map, we’re only interested in groups with multiple tabs. So we need to filter the map:

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function filterMapByValues(map, f) {
    const filtered = new Map()

    for (let [k, v] of map) {
        if (f(v))
            filtered.set(k, v)
    }

    return filtered
}

We end up with URL -> group map where each group contains at least 2 tabs:

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var dupesByUrl = filterMapByValues(groupTabsBy(tabs, tab => tab.url),
    tabs => tabs.length > 1)

Now from each group we have to close all tabs except one:

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function closeDupes(dupeMap) {
    for (let [k, tabs] of dupeMap) {
        const ids = tabs.slice(1).map(tab => tab.id)
        console.info("Removing", ids.length, "duplicates for key", k)
        ids.forEach(id => browser.tabs.remove(id))
    }
}

closeDupes(dupesByUrl)

Finding duplicates tabs by title is analogous:

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var dupesByTitle = filterMapByValues(groupTabsBy(tabs, tab => tab.title),
    tabs => tabs.length > 1)

Before closing these we should be little careful since two different (non-duplicate) tabs may share the same title – especially if the title is not very distinctive.

Close tabs by URL or by title

When researching a topic I usually open many tabs on a single domain or with a certain keyword in their title. So here is a code which can find and close these.

By URL:

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tabs.filter(tab => tab.url.includes("//mail.google.com/")).forEach(tab => {
    console.log(tab.title, tab.url)
    // Uncomment to close.
    //browser.tabs.remove(tab.id)
})

By title:

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tabs.filter(tab => tab.title.toLowerCase().includes("google")).forEach(tab => {
    console.log(tab.title, tab.url)
    // Uncomment to close.
    //browser.tabs.remove(tab.id)
})