Download url chrome extension

Question

I am trying to download a url by writing code for chrome extension. Here is the myscript.js file:

chrome.downloads.download(
    {url: 'http://www.iana.org/_img/iana-logo-pageheader.png',
     saveAs: true
    },
    function(res){alert(res);});

and here is my manifest.json

{
  "name": "My extension",
  "version": "1.0",
  "manifest_version":2,
  "background_page": "background.html",
  "browser_action": {
    "name": "Manipulate DOM",
    "icons": ["icon.png"],
    "default_icon": "icon.png"
  },
  "permissions": ["downloads",
    "tabs", "http://*/*","https://*/*"
  ],
  "content_scripts": [
    {
      "matches": [ "http://*/*", "https://*/*"],
      "js": ["jquery.js","d3.v2.js","myscript.js"],
      "run_at": "document_end"
    }
  ]
}

but the console is showing the error "Cannot call method 'download' of undefined". Please help me.

Answer 1

The documentation for chrome.downloads clearly states that the "API is still under development. It is only available for Chrome users on the dev early release channel." (emphasis mine, currently at Chrome 23).

To use the API, you need to get a dev or canary build of Chrome (see this page for download links).

Another way to solve the problem is by not using the chrome.downloads API. I've been using the following method to create downloads, and it works like a charm (it works anywhere: Content script / background page / popup / whatever):

var a = document.createElement('a');
a.href = 'http://www.iana.org/_img/iana-logo-pageheader.png';
a.download = 'iana-logo-pageheader.png'; // Filename
a.click();                               // Trigger download

a.click() causes Chrome to follow the link.
The download attribute causes Chrome to download the target, and suggest the attribute's value as a file name in the Save As dialog.

This feature is not limited to Chrome extensions, you can also use it in an ordinary web page. Have a look at this demo: http://jsfiddle.net/dEeHF/.