kfiil

//For an rfc4122 version 4 compliant solution, this one-liner(ish) solution is the most compact I could come up with
//http://stackoverflow.com/a/2117523
'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
    var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);
    return v.toString(16);
});

//http://guid.us/GUID/JavaScript
function S4() {
    return (((1+Math.random())*0x10000)|0).toString(16).substring(1); 

kfiil

/**
  Test for "value is null or undefined" is
**/
if ( some_variable == null ){
  // some_variable is either null or undefined
}

// So these two lines are equivalent:
if ( typeof(some_variable) !== "undefined" && some_variable !== null ) {}
if ( some_variable != null ) {}

kfiil

// Source: https://stackoverflow.com/a/12550320

function pad(n){return n<10 ? '0'+n : n}

/* use a function for the exact format desired... */
function ISODateString(d){
    function pad(n){return n<10 ? '0'+n : n}
    return d.getUTCFullYear()+'-'
    + pad(d.getUTCMonth()+1)+'-'
    + pad(d.getUTCDate())+'T'