nobuoka/manifest.json

## manifest.json
{
  "name": "Extension for test",
  "version": "1.0",
  "manifest_version": 2,
  "description": "for test of alert, confirm and prompt functions",
  "browser_action": {
    "default_popup": "popup.html"
  },
  "permissions": [
  ]
}

## popup.html
<!DOCTYPE html>
<html>
  <head>
    <title>test</title>
    <script src="popup.js"></script>
  </head>
  <body>
    <form id="test-form">
      <div>
        <input type="submit" id="test-input">
      </div>
    </form>
  </body>
</html>

## popup.js
document.addEventListener( "DOMContentLoaded", function listener( evt ) {
    var e = document.getElementById( "test-form" );
    e.addEventListener( "submit", function listener( evt ) {
    //    confirm( "ok?" );
    }, false );
    e = document.getElementById( "test-input" );
    e.addEventListener( "click", function listener( evt ) {
        confirm( "ok?" );
    }, false );
}, false );

setTimeout( function callback() {
    confirm( "okok?" );
}, 2000 );
	{
	"name": "Extension for test",
	"version": "1.0",
	"manifest_version": 2,
	"description": "for test of alert, confirm and prompt functions",
	"browser_action": {
	"default_popup": "popup.html"
	},
	"permissions": [
	]
	}