Using Vue's v-if statement to determine if a variable is either empty or null

Question

Using Vue's v-if statement to determine if a variable is either empty or null

Using a v-if statement to display certain HTML only if the archiveNote variable is not empty or null.

<div v-if="archiveNote === null || archiveNote ===''" class="form-check ml-3" id="include-note-div">

Here is how it's implemented

export default {
    name: "ConfirmReleaseFilesModal",
    props: {
        archiveName: String,
        archiveNote: String
    },

This information is then passed from another Vue file

<confirm-release-files-modal
    v-if="showConfirmReleaseFilesModal"
    @cancel="closeModal"
    @confirmAndEmail="releaseAction"
    @confirmNoEmail="releaseAction"
    :archive-name="archiveName"
    :archive-note ="archiveNote"
>
</confirm-release-files-modal>

The HTML content still appears even when the archiveNote variable is logged as empty

javascript vue.js vuejs2 vue-component

Answer 1

Answer №1

If you'd like to display the <div> only when it is considered truthy (not empty/null/etc.), you can achieve this with the following code snippet:

<div v-if="archiveNote">

This functions similarly to using the double bang:

<div v-if="!!archiveNote">

Both of these statements interpret all 8 of JavaScript's falsy values as false:

false
null
undefined
0
-0
NaN
''
0n (BigInt)

Everything else will equate to true. Therefore, if your variable does not match any of these falsy values, it will be regarded as truthy and the v-if statement will render the element.

Below is a demonstration showcasing these concepts along with some examples of truthy values:

new Vue({
  el: "#app",
  data() {
    return {
      falsy: {
        'null': null,
        'undefined': undefined,
        '0': 0,
        '-0': -0,
        '\'\'': '',
        'NaN': NaN,
        'false': false,
        '0n': 0n
      },
      truthy: {
        '[]': [],
        '{}': {},
        '\'0\'': '0',
        '1': 1,
        '-1': -1,
        '\' \'': ' ',
        '\'false\'': 'false',
        '5': 5
      }
    }
  }
});

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}
#falsy, #truthy {
  display: inline-block;
  width: 49%;
}
.label {
  display: inline-block;
  width: 80px;
  text-align: right;
}
code {
  background: #dddddd;
  margin: 0 3px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <div id="falsy">
    Falsy:
    <div v-for="(test, label) in falsy">
      <div class="label">{{ label }}</div>
      <code v-if="test">true</code>
      <code v-else>false</code>
    </div>
  </div>

  <div id="truthy">
    Truthy examples:
    <div v-for="(test, label) in truthy">
      <div class="label">{{ label }}</div>
      <code v-if="test">true</code>
      <code v-else>false</code>
    </div>
  </div>
</div>

Answer 2

If you'd like to display the <div> only when it is considered truthy (not empty/null/etc.), you can achieve this with the following code snippet:

<div v-if="archiveNote">

This functions similarly to using the double bang:

<div v-if="!!archiveNote">

Both of these statements interpret all 8 of JavaScript's falsy values as false:

false
null
undefined
0
-0
NaN
''
0n (BigInt)

Everything else will equate to true. Therefore, if your variable does not match any of these falsy values, it will be regarded as truthy and the v-if statement will render the element.

Below is a demonstration showcasing these concepts along with some examples of truthy values:

new Vue({
  el: "#app",
  data() {
    return {
      falsy: {
        'null': null,
        'undefined': undefined,
        '0': 0,
        '-0': -0,
        '\'\'': '',
        'NaN': NaN,
        'false': false,
        '0n': 0n
      },
      truthy: {
        '[]': [],
        '{}': {},
        '\'0\'': '0',
        '1': 1,
        '-1': -1,
        '\' \'': ' ',
        '\'false\'': 'false',
        '5': 5
      }
    }
  }
});

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}
#falsy, #truthy {
  display: inline-block;
  width: 49%;
}
.label {
  display: inline-block;
  width: 80px;
  text-align: right;
}
code {
  background: #dddddd;
  margin: 0 3px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <div id="falsy">
    Falsy:
    <div v-for="(test, label) in falsy">
      <div class="label">{{ label }}</div>
      <code v-if="test">true</code>
      <code v-else>false</code>
    </div>
  </div>

  <div id="truthy">
    Truthy examples:
    <div v-for="(test, label) in truthy">
      <div class="label">{{ label }}</div>
      <code v-if="test">true</code>
      <code v-else>false</code>
    </div>
  </div>
</div>

Answer 3

Answer №2

Having encountered an issue with the accepted answer, I decided to provide my own solution.

In my case, even though my object appeared empty, it was still considered as truthy.

Note: Since my object was in the form of an array (similar to JSON), I found using Object.keys()>0 to be a more reliable method for checking if the array is empty. This approach may only be applicable to arrays based on my understanding.

{
    "__v_isShallow": false,
    "__v_isRef": true,
    "_rawValue": {},
    "_value": {}
}

Hence, a preferable solution would be to verify with

v-if="Object.keys(archiveNote).length > 0"

or

Answer

Here's a code snippet illustrating the same:


const app = Vue.createApp({
    data() {
        return {
            archiveNote: ['Note 1', 'Note 2', 'Note 3'] // Example array
        };
    }
});

app.mount('#app');

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Vue.js Demo</title>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/vue/3.4.8/vue.global.min.js"></script>
</head>
<body>
    <div id="app">
        <!-- Using v-if with Object.keys(archiveNote) > 0 -->
        <div v-if="Object.keys(archiveNote).length > 0">
            Display something because archiveNote is not empty.
        </div>

        <!-- Using v-if=archiveNote.length -->
        <div v-if="archiveNote.length">
            Display something because archiveNote is not empty.
        </div>
        
    </div>

    <script src="app.js"></script>
</body>
</html>

Answer 4

Having encountered an issue with the accepted answer, I decided to provide my own solution.

In my case, even though my object appeared empty, it was still considered as truthy.

Note: Since my object was in the form of an array (similar to JSON), I found using Object.keys()>0 to be a more reliable method for checking if the array is empty. This approach may only be applicable to arrays based on my understanding.

{
    "__v_isShallow": false,
    "__v_isRef": true,
    "_rawValue": {},
    "_value": {}
}

Hence, a preferable solution would be to verify with

v-if="Object.keys(archiveNote).length > 0"

or

Answer

Here's a code snippet illustrating the same:


const app = Vue.createApp({
    data() {
        return {
            archiveNote: ['Note 1', 'Note 2', 'Note 3'] // Example array
        };
    }
});

app.mount('#app');

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Vue.js Demo</title>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/vue/3.4.8/vue.global.min.js"></script>
</head>
<body>
    <div id="app">
        <!-- Using v-if with Object.keys(archiveNote) > 0 -->
        <div v-if="Object.keys(archiveNote).length > 0">
            Display something because archiveNote is not empty.
        </div>

        <!-- Using v-if=archiveNote.length -->
        <div v-if="archiveNote.length">
            Display something because archiveNote is not empty.
        </div>
        
    </div>

    <script src="app.js"></script>
</body>
</html>

Answer 5

Answer №3

The reason for this issue could stem from the incorrect variable assignment in the parent component, where you are using :archive-name="archiveName" instead of :archiveName="archiveName".

Answer 6

The reason for this issue could stem from the incorrect variable assignment in the parent component, where you are using :archive-name="archiveName" instead of :archiveName="archiveName".

Using Vue's v-if statement to determine if a variable is either empty or null

Answer №1

Answer №2

Answer

Answer №3

Similar questions

Retrieving information from a virtual document in a 'pre' save hook using Mongoose

Acquire dynamically loaded HTML content using Ajax within a WebView on an Android

Node.js meets Blockly for a dynamic programming experience

Issue with loading Babel preset in a monorepo setup

Is employing absolute paths in our confidential Node dependencies a good idea?

Attempting to import a npm module that is not defined

What is the most effective method for disregarding undefined values?

Having trouble displaying the time in the middle square when pressing TouchableOpacity in React Native?

Shuffle array elements in JavaScript

Unable to fetch the identification number from the database

encountering difficulties when trying to install npm packages in node.js

What is the best way to retrieve information from a database based on an ID?

Prevent rendering a file in node.js using ejs if it cannot be found

I have the ability to effectively open a modal whenever necessary, but I struggle with closing it afterwards

Develop universal style classifications for JSS within material-ui

An error was encountered stating "TypeError: Unable to call function on undefined object while attempting to utilize a JSON object

Retrieve data from MongoDB using the unique identifier (_id) and additional conditions with Express

Create a new cookie in Angular if it is not already present

Guide to displaying or hiding elements based on the number of selected checkboxes

Tips for eliminating whitespace from an input field and then updating the field with the trimmed value