javascript - Chrome Extension: query tabs async - Stack Overflow

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I have two variables being set to the "return value" of functions, these functions are to get the URL of a tab, and a reference to the actual tab object, and store them in variables. I have some code:

function init(){
    var url = getUrl();
    var tab = getTab();
}

function getUrl(){
    var tablink;
    chrome.tabs.query({currentWindow: true, active: true},function(tabs){
        tablink = tabs[0].url;
        return tablink;
    });

}

function getTab(){
    var tab;
    chrome.tabs.query({currentWindow: true, active: true},function(tabs){
        tab = tabs[0];
    });
    return tab;
}

Why is it that, URL is undefined, though I'm returning the URL from within the callback function, yet when I return tab from outside of the callback, it returns fine, as though this were a synchronous call. I have a screenshot of this phenomenon in the debugger. I'm trying my best to learn how to deal with the asynchronous methods in chrome, but this is very confusing. Can someone explain this behavior to me?

I have two variables being set to the "return value" of functions, these functions are to get the URL of a tab, and a reference to the actual tab object, and store them in variables. I have some code:

function init(){
    var url = getUrl();
    var tab = getTab();
}

function getUrl(){
    var tablink;
    chrome.tabs.query({currentWindow: true, active: true},function(tabs){
        tablink = tabs[0].url;
        return tablink;
    });

}

function getTab(){
    var tab;
    chrome.tabs.query({currentWindow: true, active: true},function(tabs){
        tab = tabs[0];
    });
    return tab;
}

Why is it that, URL is undefined, though I'm returning the URL from within the callback function, yet when I return tab from outside of the callback, it returns fine, as though this were a synchronous call. I have a screenshot of this phenomenon in the debugger. I'm trying my best to learn how to deal with the asynchronous methods in chrome, but this is very confusing. Can someone explain this behavior to me?

• javascript
• google-chrome
• asynchronous
• google-chrome-extension

Share Improve this question Follow edited Feb 15, 2014 at 11:20 BenMorel 36.6k5151 gold badges205205 silver badges336336 bronze badges asked Nov 17, 2013 at 8:57 aclave1aclave1 1,7121818 silver badges2929 bronze badges 1

• 1 possible duplicate of After calling chrome.tabs.query, the results are not available – Rob W Commented Nov 17, 2013 at 9:50

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1 Answer 1

Sorted by: Reset to default 7

As you already said the chrome.tabs.query function is asynchronous. Because of this, you cannot rely on return, instead you have to use callbacks. The documentation for Chrome extension explains it quite well: http://developer.chrome./extensions/overview.html#sync-example

So in your case, something like this might work (depends on what you want to later with it).

var url, tab;
function init(){
    chrome.tabs.query({currentWindow: true, active: true},function(tabs){
       url = tabs[0].url;
       tab = tabs[0];
       //Now that we have the data we can proceed and do something with it
       processTab();
    });
}

function processTab(){
    // Use url & tab as you like
    console.log(url);
    console.log(tab);
}

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