about chrome.tabs.executeScript( id,details, callback)

Question

This function has a callback like function(array of any result) {...};

But I don't know what is the result means.

For example,

chrome.tabs..executeScript(null,
   {code:"var x = 10"},
   function(){});

how to return the x to the callback?

Pernik

Look at this question in Google Groups. – Rheumatoid

Answer 1

The result of a script is the last expression being evaluated. So in your example you could use:

chrome.tabs.executeScript( null, {code:"var x = 10; x"},
   function(results){ console.log(results); } );

This will log [10] to the extension's console.

results is actually an array of values because if the page has more than one frame you can specify that the script should be injected in each one of them and get the result of all injections. See the specification for executeScript. If you don't specify allFrames: true, then results will always be a single element array.

Rockefeller

I have this chrome.tabs.executeScript( null, {code:"var x = 10; x"}, function(results){ alert(results); } ); but gets undefined as an alert. Do you have any clue why this might happen? – Kinsler

@user1032613 that will happen if your extension doesn't have permissions to execute a script on the current tab. Make sure the domain is included in the permissions setting of your manifest.json – Rockefeller

Thanks! And I just realized that, modifications made to manifest.json will only take effect after I reinstall the extension. – Kinsler

@user1032613 You can reload the extension by turning on the developer mode in chrome://extensions. or press ctrl-R – Hachmin

For me, the alert immediately disappears? – Polychromy

Note that the result will too be null if the code throws an error. – Newberry

@virus No. You must be very careful with the code to be executed, if you want the results. Use try..catch and always return a structured clonable type (a string will do, an error won't) – Edik