Vue.js v-if / v-else


Assuming we have a Vue.js instance defined as:

var vm = new Vue({
    el: '#example',
    data: {
        a: true,
        b: false

You can conditionally render any html element by including the v-if directive; the element that contains v-if will only render if the condition evaluates to true:

<!-- will render 'The condition is true' into the DOM -->
<div id="example">
    <h1 v-if="a">The condition is true</h1>

The <h1> element will render in this case, because the variable 'a' is true. v-if can be used with any expression, computed property, or function that evaluates to a boolean:

<div v-if="0 === 1">                  false; won't render</div>
<div v-if="typeof(5) === 'number'">   true; will render</div>

You can use a template element to group multiple elements together for a single condition:

<!-- in this case, nothing will be rendered except for the containing 'div' -->
<div id="example">
    <template v-if="b">
        <p>Paragraph 1</p>
        <p>Paragraph 2</p>

When using v-if, you also have the option of integrating a counter condition with the v-else directive. The content contained inside the element will only be displayed if the condition of the previous v-if was false. Note that this means that an element with v-else must appear immediately after an element with v-if.

<!-- will render only 'ELSE' -->
<div id="example">
    <h1 v-if="b">IF</h1>
    <h1 v-else="a">ELSE</h1>

Just as with v-if, with v-else you can group multiple html elements together within a <template>:

<div v-if="'a' === 'b'"> This will never be rendered. </div>
<template v-else>
      <li> You can also use templates with v-else. </li>
      <li> All of the content within the template </li>
      <li> will be rendered. </li>