Checking for matching items in two JS arrays

arrayValueMatch.js

function arrayValueMatch( array1, array2 ) {
  var length = array1.length, match = false;
  for ( i=0; i<length; i+=1 ) {
    if ( array2.indexOf( array1[i] ) > -1 ) {
      match = true;
      break;
    }
  }
  return match;
}

You could get rid of some typing with:

function arrayMatchesAny(a, b) { 
  for(var i=0; i<a.length; i++) 
    if (b.indexOf(a[i]) > -1) return true
  return false
}

The same logic you have, but multiple returns lets you skip the break and stored value. Also, if you're only using length once, you may as well only reference it once. Not sure if that affects performance, but it's safe to assume it doesn't.

You could also get clever and extend the array object:

Array.prototype.containsAny = function (other) { 
  for (var i=0; i < this.length; i++) if (other.indexOf(this[i]) > -1) return true; 
  return false; 
}

Or use some, an existing array method:

var a = [1,2,3,4], b = [7, 6, 5, 4]
a.some(function (e) { return b.indexOf(e) > -1; })

indexOf is as good as you're going to get (O(n^2)) unless you keep the arrays sorted and use a binary search to lookup each element of a in b (O(n log n)).