vendor/dummy-deps/rx.js
function arrayIndexOfComparer(array, item, comparer) {
    for (var i = 0, len = array.length; i < len; i++) {
      if (comparer(array[i], item)) { return i; }
    }
    return -1;
  }
function arrayIndexOfComparer(array, item, comparer) {
    for (var i = 0, len = array.length; i < len; i++) {
      if (comparer(array[i], item)) { return i; }
    }
    return -1;
  }
function arrayIndexOfComparer ( array , item , comparer ) { for ( var i = 0 , len = array . length ; i < len ; i ++ ) { if ( comparer ( array [ i ] , item ) ) { return i ; } } return - 1 ; }
Swap out for Array.findIndex
Swap out for Array . findIndex