How to perform set related operations?

hualin_yip · November 8th, 2004, 07:10 PM

Hi, Does anyone have recommendation of the best way to achieve the following in javascript?
I have two set, one contains some numbers, the other contains some other numbers, e.g
set 1: contains 1, 3, 4, 5
set 2: contains 1, 2, 3, 4, 5
I want to know if set 1 contains all the numbers in set 2, if not, it is an error and I will alert the user.
What I really wanted to achieve is that I have several (identical) selection boxes on the left, and several (identical) selection boxes on the right, and I am mapping each item from the left selection box to something in the right selection boxes. And I want to make sure each and every item in the left selection box is chosen to be mapped to something on the right before I click submit.
Thanks for your help.

joefawcett · November 9th, 2004, 08:00 AM

Can't think of anything other than nested loops:

Code:

function isSubset(set, subset)
{
  for (var i = 0 ; i < subset.length; i++)
  {
    var currentItem = subset[i];
    var bFound = false;
    for (var j = 0; j < set.length; j++)
    {
      if (set[j] == currentItem)
      {
        bFound = true;
        break;
      }  
    }
    if (!bFound)
    {
      return false;
    }
  }
  return true;
}

Checks if all values in second parameter are in first.

Code:

var arr1 = [1, 2, 3, 4];
var arr2 = [1, 2, 3, 4, 6];
alert(isSubset(arr2, arr1));

--

Joe (Microsoft MVP - XML)