Create unique id with javascript

annotated.js

// Based on this answer: https://stackoverflow.com/a/10734934/1650200
// Compressed version is 139 bytes - Generated using http://refresh-sf.com/

function g(){
  var s = String.fromCharCode,    // Shorthand for String.fromCharCode()
      r = Math.random,            // Shorthand for Math.random()
      i = s(~~((r()*25)+65)),     // Generate a letter to start the id (for DOM friendliness)
      a = b = 0;                  // Declare variable 'a' and set counter to 0
  for(;b<32;a = ~~((r()*42)+48))  // While less the id's length is less than 32, generate a character
    a<58||a>64 ?                  // If the generated character is not a special symbol,
      (i+=s(a),b++)               // Add to the end of id, increment length counter by 1
    : a;                          // Otherwise, do nothing
  return i;                       // Return the id
}

GenerateUniqueId.js

function g(){for(var r=String.fromCharCode,n=Math.random,o=r(~~(25*n()+65)),a=b=0;b<32;a=~~(42*n()+48))58>a||a>64?(o+=r(a),b++):a;return o}