javascript - 如何计算具有给定属性值的数组中的对象(Angular-Firebase Realtime)

Question

https://prnt.sc/qo0iig

我想在“状态”为真时对其进行计数。我该怎么办？

组件.ts

getAttDetails(ıd){
        this.afAuth.user.subscribe(user => this.serviceCourses.getAttDetails(ıd,user).subscribe(detail => console.log(detail)));
      }

服务类(class)

getAttDetails(ıd,user:firebase.User){
    return  this.db.list('/denemeDersler/'+ıd+'/attendance/'+user.uid).snapshotChanges().pipe(map(changes => changes
      .map(c => ({key: c.payload.key, ...c.payload.val()}))));
   }

Answer 1

你可以做这样的事情

假设您的数据集是这样的

let arr = [{key : '2020-01-15', statu : true},{key : '2020-01-11', statu : true},{key : '2020-01-10', statu : false}]

let count = 0;
arr.map(item=> { if(item.statu === true){ count++ } })
console.log(count) // output : 2