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

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