Checking postMessage host

handleMessage.js

normalize = function(url) {
    var parser;
    parser = document.createElement('a');
    parser.href = url;
    return "" + parser.protocol + "//" + parser.host;
};

function handleMessage(e) {
    // ...

    if (normalize(e.origin) !== 'https://clef.io') {
        return;
    }

    // ...
}

$(window).on('message', handleMessage);