javascript Pad && uuid

1 pad

String.prototype.PadLeft = function(totalWidth, paddingChar)
{
 if ( paddingChar != null )
 {
  return this.PadHelper(totalWidth, paddingChar, false);
 } else {
  return this.PadHelper(totalWidth, ' ', false);
 }
}
String.prototype.PadRight = function(totalWidth, paddingChar)
{
 if ( paddingChar != null )
 {
  return this.PadHelper(totalWidth, paddingChar, true);
 } else {
  return this.PadHelper(totalWidth, ' ', true);
 }
 
}
String.prototype.PadHelper = function(totalWidth, paddingChar, isRightPadded)
{

 if ( this.length < totalWidth)
 {
  var paddingString = new String();
  for (i = 1; i <= (totalWidth - this.length); i++)
  {
   paddingString += paddingChar;
  }

  if ( isRightPadded )
  {
   return (this + paddingString);
  } else {
   return (paddingString + this);
  }
 } else {
  return this;
 }
}

 2 uuid

function uuid()
{
    return '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);
    });
}

function uuid4()
{
  function hex (s, b)
  {
    return s +
      (b >>> 4   ).toString (16) +  // high nibble
      (b & 0b1111).toString (16);   // low nibble
  }

  let r = crypto.getRandomValues (new Uint8Array (16));

  r[6] = r[6] >>> 4 | 0b01000000; // Set type 4: 0100
  r[8] = r[8] >>> 3 | 0b10000000; // Set variant: 100

  return r.slice ( 0,  4).reduce (hex, '' ) +
         r.slice ( 4,  6).reduce (hex, '-') +
         r.slice ( 6,  8).reduce (hex, '-') +
         r.slice ( 8, 10).reduce (hex, '-') +
         r.slice (10, 16).reduce (hex, '-');
}

function generateUUID() { // Public Domain/MIT
    var d = new Date().getTime();//Timestamp
    var d2 = (performance && performance.now && (performance.now()*1000)) || 0;//Time in microseconds since page-load or 0 if unsupported
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
        var r = Math.random() * 16;//random number between 0 and 16
        if(d > 0){//Use timestamp until depleted
            r = (d + r)%16 | 0;
            d = Math.floor(d/16);
        } else {//Use microseconds since page-load if supported
            r = (d2 + r)%16 | 0;
            d2 = Math.floor(d2/16);
        }
        return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16);
    });
}

参考:

https://stackoverflow.com/questions/105034/create-guid-uuid-in-javascript?page=1&tab=votes#tab-top