#1
Code:
/**
 * Function to produce UUID.
 */
function generateUUID()
{
    var d = new Date().getTime();
    
    if( window.performance && typeof window.performance.now === "function" )
    {
        d += performance.now();
    }
    
    var uuid = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'.replace(/[xy]/g, function(c)
    {
        var r = (d + Math.random()*16)%16 | 0;
        d = Math.floor(d/16);
        return (c=='x' ? r : (r&0x3|0x8)).toString(16);
    });

return uuid;
}

/**
 * Generate new key and insert into input value
 */
$( '#keygen' ).on('click',function()
{
    $( '#apikey' ).val( generateUUID() );
});