Maybe I am not understanding what you want to do, but why not split the string on the comma?
if you do this:
var array = str.split(",");
for(wordIndex in array)
//array[wordIndex] is each individual address
//run REGEX on each one to determine if it is valid or whatever you are planning
by Ezzaral: Added code tags. Please use them to format any code that you post.
Better yet... str.split(/\s*,\s*/) which will get rid of white spaces before and after comma... This would take care of "ab,c, de , g,h,i" as an array with elements ["ab", "c", "de", "g", "h", "i"] instead of ["ab", "c", " de ", " g", "h", i"] as the suggested above post. Though, the above post is going on the right track. :)