utility_functions.js

// returns a string such as "2020-10-13" for the given seconds since epoch or the current day if secs is undefined
function getDateNow(secs) {
    let d
    if (secs === undefined) { d = new Date() } else { d = new Date(secs) }
    let datenow  = [  d.getFullYear(),  ('0' + (d.getMonth() + 1)).slice(-2),  ('0' + d.getDate()).slice(-2)].join('-');
    return datenow
}

// returns a string such as "14:25" for the given seconds since epoch or the current time if secs is undefined
function getTimeNow(secs) {
    let d
    if (secs === undefined) { d = new Date() } else { d = new Date(secs) }
    let datenow  = [    ('0' + d.getHours() ).slice(-2),  ('0' + d.getMinutes()).slice(-2)].join(':');
    return datenow
}

// returns seconds since epoch for the given date and time
function getSecondsForDatetime( date, time ) {  // ex getSecondsForDatetime("2019-07-07", "04:15")
    let timestring = date+"T"+time
    let seconds = new Date(timestring).getTime();
    return seconds
}

// takes a string and returns it with all areas of multiple whitspace reduced to one space
function extraSpacesBeGone(string){
    return string.replace(/\s{2,}/g, ' ');

}

// a few different uuid creation functions
// ***these should not be concidered full proof or meeting any standards

function generateUUID() {
    let d = new Date().getTime();
    if (typeof performance !== 'undefined' && typeof performance.now === 'function'){
        d += performance.now(); //use high-precision timer if available
    }
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
        let r = (d + Math.random() * 16) % 16 | 0;
        d = Math.floor(d / 16);
        return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16);
    });
}


// source:  http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript/21963136#21963136
function anotherGenerateUUID () {
    var _lut = [];
	for ( var i = 0; i < 256; i ++ ) {
		_lut[ i ] = ( i < 16 ? '0' : '' ) + ( i ).toString( 16 );
	}

    var d0 = Math.random() * 0xffffffff | 0;
    var d1 = Math.random() * 0xffffffff | 0;
    var d2 = Math.random() * 0xffffffff | 0;
    var d3 = Math.random() * 0xffffffff | 0;
    var uuid = _lut[ d0 & 0xff ] + _lut[ d0 >> 8 & 0xff ] + _lut[ d0 >> 16 & 0xff ] + _lut[ d0 >> 24 & 0xff ] + '-' +
        _lut[ d1 & 0xff ] + _lut[ d1 >> 8 & 0xff ] + '-' + _lut[ d1 >> 16 & 0x0f | 0x40 ] + _lut[ d1 >> 24 & 0xff ] + '-' +
        _lut[ d2 & 0x3f | 0x80 ] + _lut[ d2 >> 8 & 0xff ] + '-' + _lut[ d2 >> 16 & 0xff ] + _lut[ d2 >> 24 & 0xff ] +
        _lut[ d3 & 0xff ] + _lut[ d3 >> 8 & 0xff ] + _lut[ d3 >> 16 & 0xff ] + _lut[ d3 >> 24 & 0xff ];

    // .toUpperCase() here flattens concatenated strings to save heap memory space.
    return uuid.toUpperCase();
}



// this one requires a browser or electron render process
function generateUUIDv4() {
  return ([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g, c =>
    (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
  );
}