polygerrit-ui/app/behaviors/async-foreach-behavior/async-foreach-behavior.html

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<script>
(function(window) {
  'use strict';

  window.Gerrit = window.Gerrit || {};

  /** @polymerBehavior Gerrit.AsyncForeachBehavior */
  Gerrit.AsyncForeachBehavior = {
    /**
     * @template T
     * @param {!Array<T>} array
     * @param {!Function} fn An iteratee function to be passed each element of
     *     the array in order. Must return a promise, and the following
     *     iteration will not begin until resolution of the promise returned by
     *     the previous iteration.
     *
     *     An optional second argument to fn is a callback that will halt the
     *     loop if called.
     * @return {!Promise<undefined>}
     */
    asyncForeach(array, fn) {
      if (!array.length) { return Promise.resolve(); }
      let stop = false;
      const stopCallback = () => { stop = true; };
      return fn(array[0], stopCallback).then(exit => {
        if (stop) { return Promise.resolve(); }
        return this.asyncForeach(array.slice(1), fn);
      });
    },
  };
})(window);
</script>