ut2/lib/internals/createReduce.js

一个现代 JavaScript 实用工具库。[点击查看在线文档]。

'use strict';

var allKeys = require('../allKeys.js');
var identity = require('../identity.js');
var isArrayLike = require('../isArrayLike.js');

function createReduce(dir) {
    function reducer(collection, iteratee, memo, initial) {
        var _keys = !isArrayLike(collection) && allKeys(collection);
        var len = (_keys || collection).length;
        var i = dir > 0 ? 0 : len - 1;
        if (!initial && len > 0) {
            memo = collection[_keys ? _keys[i] : i];
            i += dir;
        }
        while (i >= 0 && i < len) {
            var currentKey = _keys ? _keys[i] : i;
            memo = iteratee(memo, collection[currentKey], currentKey, collection);
            i += dir;
        }
        return memo;
    }
    var reduce = function (collection, iteratee, initialValue) {
        if (iteratee === void 0) { iteratee = identity; }
        var initial = arguments.length >= 3;
        return reducer(collection, iteratee, initialValue, initial);
    };
    return reduce;
}

module.exports = createReduce;