This code works for me:
function load() {
var channels = "";
var keywords = "";
chrome.storage.local.get('channels', function (result) {
channels = result.channels;
alert(result.channels);
$("#channels").val(channels);
});
}
Chrome.storage.local.get() returns an object with items in their key-value mappings, so you have to use the index of the key in your search pattern.
IMP:
Thanks to Rob for identifying: Chrome.storage.local.get() is asynchronous, you should modify your code to ensure they work after callback() is successful.
Let me know if you need more information.