在 Firebase Object 上使用 Object.keys() 而不是 .length

Question

如何使用 Object.keys() 来纠正这个片段？ 当评论 id 是数字时，代码可以正常工作。 现在如何使它与来自 firebase 的自动生成的 ID 一起工作。

（数据结构如下）

 ngOnInit() { this.route.params.pipe(switchMap((params: Params) => this.dishservice.getDish(params['id']))).subscribe(dish => { this.dish = dish this.favorite = this.favoriteService.isFavorite(this.dish.id); //compute the average of ratings and render the number of comments this.numcomments = this.dish.comments.length; let total =0; this.dish.comments.forEach(comment =>total += comment.rating); this.avgstars = (total/this.numcomments).toFixed(2); }, errmess => this.errMess = <any>errmess); }

Answer 1

尝试这个

const commentIds  = Object.keys(this.dish.comments);
this.numcomments =  commentIds.length;           
let total = 0; 
commentIds.forEach(commentId => total += this.dish.comments[commentId].rating); 
this.avgstars = (total/this.numcomments).toFixed(2);