lodash-es/_setData.js

import baseSetData from './_baseSetData';
import now from './now';

/** Used to detect hot functions by number of calls within a span of milliseconds. */
var HOT_COUNT = 150,
    HOT_SPAN = 16;

/**
 * Sets metadata for `func`.
 *
 * **Note:** If this function becomes hot, i.e. is invoked a lot in a short
 * period of time, it will trip its breaker and transition to an identity
 * function to avoid garbage collection pauses in V8. See
 * [V8 issue 2070](https://bugs.chromium.org/p/v8/issues/detail?id=2070)
 * for more details.
 *
 * @private
 * @param {Function} func The function to associate metadata with.
 * @param {*} data The metadata.
 * @returns {Function} Returns `func`.
 */
var setData = (function() {
  var count = 0,
      lastCalled = 0;

  return function(key, value) {
    var stamp = now(),
        remaining = HOT_SPAN - (stamp - lastCalled);

    lastCalled = stamp;
    if (remaining > 0) {
      if (++count >= HOT_COUNT) {
        return key;
      }
    } else {
      count = 0;
    }
    return baseSetData(key, value);
  };
}());

export default setData;