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JavaScript: Next Unique ID Function




Unique ID generation is used in JavaScript application in many places. For example giving the unique id to DOM element or may be using it to some data structure for storing in memory, where it can be use latter.



Most of the implementation I see is just defining the integer and increasing it on every call. But it is potentially candidate to integer overflow issue, which can cause errors in many edge case scenario.



var nextUid = (function(){
  var idCounter = 0; //integer counter
  return function (prefix) {
     //counter increment on every call, and it can run into integer overflow issue
     var id = ++idCounter; 
     return String(prefix == null ? '' : prefix) + id;
   }
})();




When I was reading through AngularJS source code, found this really good implementation of unique ID generation. Below is the extracted and updated version of the same, so you can use it independently.



/**
 A consistent way of creating unique IDs in angular. The ID is a sequence of alpha numeric
 characters such as '012ABC'. The reason why we are not using simply a number counter is that
 the number string gets longer over time, and it can also overflow, where as the nextId
 will grow much slower, it is a string, and it will never overflow.
 
 @returns an unique alpha-numeric string
 */
var nextUid = (function(){
  var uid = ['0','0','0'];
  return function() {
    var index = uid.length,
        digit;

    while(index) {
      index--;
      digit = uid[index].charCodeAt(0);
      if (digit == 57 /*'9'*/) {
        uid[index] = 'A';
        return uid.join('');
      }
      if (digit == 90  /*'Z'*/) {
        uid[index] = 'a';
        return uid.join('');
      } 

      if (digit == 122 /*'z'*/) { 
        uid[index] = '0';
      } else {
        uid[index] = String.fromCharCode(digit + 1);
        return uid.join('');
      }
    }
    uid.unshift('0');
    return uid.join('');
  }
})();

//output: "001", "002", "003", "008", "009", "00A", "00B", .., "01s", "01t", "01u", "01v" ..etc




Benefited of using this function is slow rate of increment, and you will never have to worry about the overflow issue. 


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