In Vue.js, a blank screen may appear if the created() lifecycle hook is not utilized or if the spread operator (...)

The situation I'm facing is that the code in this example results in a blank screen, as shown in this jsfiddle. Even elements unrelated to the loop are not being displayed.

Here's a snippet of the HTML:

<div id="app">
  <button @click="objectFromApi">
    run objectFromApi function
  </button>
  <div
    v-for="obj in myObject[0].results"
     :key="obj.id"
  >
    <p>
      {{ obj.message }}
    </p>
  </div>
</div>

This is a part of the JavaScript:

new Vue({
  el: "#app",
  data: {
    myObject: []
  },
  methods: {
    objectFromApi: function(){
        this.myObject.push(
        {
          "count": 5,
          "results": [
            {
              "id": 1,
              "message": "object 1"
            },
            {
              "id": 2,
              "message": "object 2"
            }
          ]
        }
      )
    }
  },

})

However, things work if:

1.)The objectFromApi function is directly called in the created lifecycle hook (which is not preferred)

created() {
  this.objectFromApi()
}

2.) Or without using the created life cycle hook by spreading out objects like this within the nested results array (also not desired):

this.myObject.push(
  ...{
    "count": 5,
    "next": "http://127.0.0.1:8000/api/someurl/?page=2",
    "previous": null,
    "results": [
      {
        "id": 1,
        "message": "object 1"
      },
      {
        "id": 2,
        "message": "object 2"
      }
    ]
  }.results
)

In option 2.), the v-for loop should be adjusted as follows:

v-for="obj in myObject"
instead of
v-for="obj in myObject[0].results"

What could possibly be wrong with the initial approach?

Answer №1

When the component initially renders, the array myObject will be empty.

While rendering, it tries to do this:

<div
  v-for="obj in myObject[0].results"
  :key="obj.id"
>

The value of myObject[0] is undefined. Trying to access the results property of undefined will cause an error during rendering. This error will result in a failed rendering process where nothing will be displayed, not even the parts that did not trigger an error.

There are several ways to solve this issue. One approach is to prefill the data with appropriate empty properties:

data: {
  myObject: [
    {
      results: []
    }
  ]
}

Alternatively, as you mentioned, you could modify the loop to use v-for="obj in myObject", and adjust objectFromApi so that only the results array is stored in myObject. Even if you decide against making this specific change, making a similar adjustment might be beneficial because the presence of [0] strongly implies there is an issue with your data model. The primary goal here is to avoid attempting to access nested objects that are non-existent. The utilization of the spread operator in the second example doesn't hold much significance.

Another option is to skip the loop in the template:

<template v-if="myObject[0]">
  <div
    v-for="obj in myObject[0].results"
    :key="obj.id"
  >
    ...
  </div>
</template>

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

Guide to creating a dynamic jQuery autocomplete feature with AJAX in a JSP application

I'm currently facing an issue with jQuery UI AutoComplete not working properly when using AJAX in my JSP file. Despite searching through various guides, I haven't been able to find a suitable solution for my problem. Could anyone provide some as ...

What is the process for retrieving paginated data from the store or fetching new data from an API service within an Angular 2 application using ngrx-effects?

After coming across this insightful question and answer about the structure of paginated data in a redux store, I found myself pondering how to implement similar principles using ngrx/store in an angular 2 application. { entities: { users: { 1 ...

Customize the header toolbar title in FullCalendar

I am using a basic fullcalendar with buttons in the headerToolbar My question is, how do I customize the titles on these buttons? https://i.sstatic.net/xAgXG.png https://i.sstatic.net/wK5IX.png For example, instead of month view I'd like it to be j ...

What is the most effective way in MongoDB to insert data only if it does not already exist in the database?

Is there an optimal way to insert data into MongoDB only if it doesn't already exist in the table? The unique field for searching is hash, which is also indexed. router.post('/', async (req, res) => { try{ var id = null const ...

Adding a picture to the webpage and saving it temporarily on the site

After exploring all options on the site, testing it rigorously and closely following the instructions provided, I am still unable to determine where exactly I went wrong. Website Link: The main goal is to upload an image and temporarily store it within t ...

Revolutionary Metadata for Nuxt.js

Does anyone have solutions for updating meta info with dynamic data? Issue We are facing problems with Nuxt and static page generation using npm run generate. Here are some of the issues we have identified: Open graph and Twitter meta tags cannot be ...

Step-by-step guide on accessing values from a JavaScript object

I have a dictionary variable declared within a script tag on an HTML page. My goal is to retrieve the values associated with the "Roads" and "Intersections" keys, which change each time the page is refreshed. By capturing these values, I can then use JavaS ...

Performing a JavaScript Axios POST request following a series of iterations using a while loop with

Just getting started with async/await and feeling a bit lost. I'm trying to figure out how to send an axios post request after a while loop finishes. Is there a way to wrap the while loop in an async function and await for it? Here's the code s ...

How can you determine the HTML element where a mouse click took place?

Is it possible in JavaScript to identify the HTML element where a mouse click occurs without having an event listener attached to the elements? Essentially, I want to be able to capture the mouse click event and determine the specific element on the page ...

How can we implement intricate looping mechanisms in hogan js?

Currently, I am in the process of familiarizing myself with expressjs. In my journey to learn this technology, I have encountered a controller that performs queries on a database and returns a JSON object with certain key-value pairs. An example of such an ...

There are no functions or classes returned when using NPM Link with the module

Welcome. Whenever I run npm link ../folder/ToFolder, it works as expected. However, when I attempt to import any function, nothing is returned. A clearer explanation I have tried importing a module that I created from another folder using npm link. When ...

What is the best method for encrypting a URL that contains AngularJS data?

Here is the URL that needs to be encrypted: <a class="btn btn-success btn-sm btn-block" href="@Url.Action("myAction", "myController")?Id={{repeat.Id}}&HistoryId={{repeat.HistoryId}}" ng-cloak>View History</a> I am seeking guidance on enc ...

Try utilizing MutationObserver to monitor changes in various nodes

I am faced with a situation where I have elements in my HTML that are dynamically populated with text from an API. My goal is to check if all these elements have a value and then trigger a function accordingly. The current code I have only allows me to obs ...

Tips for updating the chosen value with jquery or javascript

I am facing a situation where I need to change the selected option in a dropdown menu using a function triggered onClick later in the application. <select id="myselect"> <option value=aa>aa</option> <option value=bb>bb</option&g ...

Transferring error message between Java and Vue.js with axios communication

Can you please provide guidance on how to properly handle and display error messages generated in the backend on the frontend? In a Java Spring backend, the code might look something like this: return new ResponseEntity<>(new Exception("This is the ...

Could Express be considered the most reliable and efficient application framework for NodeJS?

While I have some experience with Express, I haven't explored many other Node-based web application frameworks. It's clear that Express is lightweight and versatile, but my usage has been limited to small experimental projects rather than large-s ...

Take action right away following a post in jQuery

I'm a beginner at using jQuery, and I have a question about displaying content immediately after making a post request. Currently, my code looks like this: $('#cur_select').on('change', function() { $.post( "getTable.php", { v ...

Having trouble testing a basic Vue example component in Laravel 5.4

I recently installed Laravel 5.4 and after running npm install, I tested a vue component example but nothing happened as expected. After running npm run dev in my project directory, the compilation was successful. However, when I ran php artisan serve, al ...

Send the response from Facebook to the flash callback on the external interface

I attempted to transfer the response from a Facebook API request obtained through the FB JS-SDK to my flash application using external interface. However, I am having trouble identifying the type of response as it displays [object object] when printed in t ...

Exploring Node.js: Managing Memory Consumption for Efficiency

I'm currently setting up multiple Node applications on one server, and I'm particularly worried about memory usage. Is there a specific amount of physical memory needed for a basic Node.js express service to run? Also, is there a method to limit ...