node.js - 如何通过使用 mongoose 查询我的 mongodb 来获取 postIds 的长度

Question

我的查询返回这个

[ { postIds:
     [ 'https://www.facebook.com/BGISaddis/photos/a.245087592543292/597050737346974/?type=3&__xts__%5B0%5D=68.ARBQb6G1JvudtWmy9B4q_1gU29zEFw6CL6rcyuzJzi6PIlEZsBuc0qOn-YlsWlYif39ANPo22eQZBHvbNid84enU80cZ3K7PAIVB7f7kufQEcsdsYmPXkMUsj_kDgWOrVn6LLAl1SrLjTsaidmaFp1iJNgUwdD2lcXdf6MuPSaMhmm5JhC4_N-fiKTIcgmGwmRs6QmuJqoAMaGthI86M21OTK2VpaJ1_Nnkz8ix5FI4aArPHDKaDNyC_iRJ_wSQJsIOJn66cHCykz00pgW0fJvfCN0vgAAQwtk2uQ_cX3wJU53cuYJkO88ngrZjzH-PBygXCHQmqGnz1Y1zxEjZll6Q&__tn__=-R',
'https://www.facebook.com/BGISaddis/photos/a.154146514970734/154145898304129/?type=3&__xts__%5B0%5D=68.ARDT-LUHFL9tKF7cZH9QVdS66xERPVvnZDNSZecJW5lT4dNnyeDJ_OzGe7s6q3_adeQGlicbBsWv61lKlGfP13QWdQKHfL1RgNHHSxEKphglroMNPGFLEYSx6Fjhh0tLA1xXEYqOAOOQ5fV_AKcIZzj3dRB_IsZAWdxOpxkf--pqkyqbV5vwrgwTA56pJ8ZKWnNMyC2Je-3FG_8EPJiHO2kcWa5QxNfoZgv_Nx7mDRzhkpHlebP4aZfnEaLU-kJQdYlb2S55O5aVSMAPtDw3wJka7-mWPA&__tn__=-R',]
    _id: 5e4bb430878c2365027fda2b } ]

这是我的代码

async function getPostLinks() {
    const posts = await Post.find().select('postIds')
    console.log(posts.length)
} 

此代码返回未定义

标签： node.jsmongodbmongoose

Answer 1

将.aggregatemongoose 与size聚合一起使用。