When attempting to update a Vue data variable, an error occurred stating that "blogItems" is not defined

I am attempting to retrieve all the posts from Firebase and store them in an array but I keep encountering the following error:

Uncaught (in promise) TypeError: Cannot read property 'blogItems' of undefined

Below is the script causing the issue:

  export default {
    data(){
      return{
        blogItems: []
      }
    },
    mounted(){
      this.getPosts();
    },
    methods:{

      getPosts(){

        database.collection('blog').doc('yP6aYXvisFbTsqtQ3MEfuyz6xYE3').collection('posts').get().then(snapshot =>{

          const posts = snapshot.docs.map(doc => doc.data())
          posts.forEach(function(post){
            this.blogItems.push(post.content)
          })
        })
        
      },

    }

  

Answer №1

In your scenario, change the reference of this in this.blogItems to posts.

You have a couple of options to fix this:

  1. Assign this to a variable and utilize it

    getPosts(){
      let tis = this;
    
     database.collection('blog').doc('yP6aYXvisFbTsqtQ3MEfuyz6xYE3').collection('posts').get().then(snapshot =>{
    
       const posts = snapshot.docs.map(doc => doc.data())
       posts.forEach(function(post){
         tis.blogItems.push(post.content)
       })
     })
    
     },
    

  1. Implement Arrow functions

     getPosts(){
    
     database.collection('blog').doc('yP6aYXvisFbTsqtQ3MEfuyz6xYE3').collection('posts').get().then(snapshot =>{
    
       const posts = snapshot.docs.map(doc => doc.data())
       posts.forEach((post) => {
         this.blogItems.push(post.content)
       })
     })
    
     },
    

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