const arr = [1,2,3,4];

Array.prototype.delayedForEach = function(callback, timeout, thisArg){
  return new Promise((reject, resolve) => {
    var i = 0,
    l = this.length,
    self = this,
    caller = function(){
      callback.call(thisArg || self, self[i], i, self);
      if (++i < l) {
        setTimeout(caller, timeout)
      } else {
        setTimeout(resolve, timeout);
      }
    };
    caller();
  });
};

await arr.delayedForEach(async (elem, index) => {
  await console.log(elem);
}, 2000);