B2G/gecko/services/sync/modules/util.js
/**
   * Build the union of two arrays. Reuse arrays if possible.
   */
Build the union of two arrays. Reuse arrays if possible.
Build the union of two arrays . Reuse arrays if possible .
function arrayUnion(foo, bar) {
    if (!foo.length)
      return bar;
    if (!bar.length)
      return foo;
    return foo.concat(Utils.arraySub(bar, foo));
  }
function arrayUnion ( foo , bar ) { if ( ! foo . length ) return bar ; if ( ! bar . length ) return foo ; return foo . concat ( Utils . arraySub ( bar , foo ) ) ; }
Build the union of two arrays.
Build the union of two arrays .