Re-write asyncMap with asyncIter

Author: ivan-tymoshenko

lib/array.js

@@ -52,57 +52,12 @@ const asyncMap = (items, fn, options = {}, done) => {
     options = DEFAULT_OPTIONS;
   }
 
-  const len = items.length || items.size;
-  const name = items.constructor.name;
-  let result = done ? new items.constructor() : null;
-  const data = common.iter(items);
-
-  if (!len || result === null) {
-    if (done) done(null, result);
-    return;
-  }
-
-  const min = options.min || DEFAULT_OPTIONS.min;
-  const percent = options.percent || DEFAULT_OPTIONS.percent;
-
-  let begin;
-  let sum = 0;
-  let count = 0;
-
-  const ratio = percent / (1 - percent);
-
-  const countNumber = () => {
-    const loopTime = Date.now() - begin;
-    const itemTime = sum / count;
-    const necessaryNumber = (ratio * loopTime) / itemTime;
-    return Math.max(necessaryNumber, min);
-  };
-
-  const next = () => {
-    const itemsNumber = count ? countNumber() : min;
-    const iterMax = Math.min(len, itemsNumber + count);
-
-    begin = Date.now();
-    for (; count < iterMax; count++) {
-      const itemResult = fn(data.next().value, count);
-      if (done) {
-        if (name === 'String') result += itemResult;
-        else if (name === 'Array') result.push(itemResult);
-        else if (name === 'Set') result.add(itemResult);
-        else result.set(itemResult);
-      }
-    }
-    sum += Date.now() - begin;
-
-    if (count < len) {
-      begin = Date.now();
-      setTimeout(next, 0);
-    } else if (done) {
-      done(null, result);
-    }
-  };
-
-  next();
+  asyncIter(items)
+    .throttle(options.percent)
+    .map(fn)
+    .toArray()
+    .then(array => done(null, array))
+    .catch(err => done(err));
 };
 
 // Asynchronous filter (iterate parallel)