1/** Used to detect hot functions by number of calls within a span of milliseconds. */
2var HOT_COUNT = 800,
3    HOT_SPAN = 16;
4
5/* Built-in method references for those with the same name as other `lodash` methods. */
6var nativeNow = Date.now;
7
8/**
9 * Creates a function that'll short out and invoke `identity` instead
10 * of `func` when it's called `HOT_COUNT` or more times in `HOT_SPAN`
11 * milliseconds.
12 *
13 * @private
14 * @param {Function} func The function to restrict.
15 * @returns {Function} Returns the new shortable function.
16 */
17function shortOut(func) {
18  var count = 0,
19      lastCalled = 0;
20
21  return function() {
22    var stamp = nativeNow(),
23        remaining = HOT_SPAN - (stamp - lastCalled);
24
25    lastCalled = stamp;
26    if (remaining > 0) {
27      if (++count >= HOT_COUNT) {
28        return arguments[0];
29      }
30    } else {
31      count = 0;
32    }
33    return func.apply(undefined, arguments);
34  };
35}
36
37module.exports = shortOut;
38