package.amd._createReduce.js Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of underscore Show documentation

JavaScript's functional programming helper library.

The newest version!

define(['./_isArrayLike', './keys', './_optimizeCb'], function (_isArrayLike, keys, _optimizeCb) {

  // Internal helper to create a reducing function, iterating left or right.
  function createReduce(dir) {
    // Wrap code that reassigns argument variables in a separate function than
    // the one that accesses `arguments.length` to avoid a perf hit. (#1991)
    var reducer = function(obj, iteratee, memo, initial) {
      var _keys = !_isArrayLike(obj) && keys(obj),
          length = (_keys || obj).length,
          index = dir > 0 ? 0 : length - 1;
      if (!initial) {
        memo = obj[_keys ? _keys[index] : index];
        index += dir;
      }
      for (; index >= 0 && index < length; index += dir) {
        var currentKey = _keys ? _keys[index] : index;
        memo = iteratee(memo, obj[currentKey], currentKey, obj);
      }
      return memo;
    };

    return function(obj, iteratee, memo, context) {
      var initial = arguments.length >= 3;
      return reducer(obj, _optimizeCb(iteratee, context, 4), memo, initial);
    };
  }

  return createReduce;

});