mongodb 分页封装（传统分页）【2020-10-30 修正】

const pageFn = ({ MATCH = [], OTHERMATCH = [], OTHERFACET = {}, FACET_KEY = {}, limit = 20, page = 1 } = {}) => {

    return [{

        $facet: {

            'list': [

                ...MATCH,

                {

                    $skip: (page - 1) * limit

                },

                {

                    $limit: limit * 1

                },

                ...OTHERMATCH.length ? OTHERMATCH : []

            ],

            'page': [

                ...MATCH,

                {

                    $count: 'count'

                }

            ],

            ...OTHERFACET

        }

    }, {

        $project: {

            list: {

                $cond: [{ $eq: [{ $size: '$list' }, 0] },

                    [], '$list'

                ]

            },

            page: {

                $cond: [{ $eq: [{ $size: '$page' }, 0] },

                    [{ count: 0 }], '$page'

                ]

            },

            count: 1,

            ...FACET_KEY

        }

    }, {

        $unwind: '$page'

    }, {

        $addFields: {

            'page.limit': limit * 1,

            'page.page': page * 1

        }

    }]

};

module.exports = pageFn