Vue v-if and v-else

To conditionally render something in Vue, you should use v-if and v-else directives. Simply pass an expression to the v-if directive, and the block will render if the expression is true. You can also use v-else, which will render if the preceeding v-if expression evaluates to a falsy value. Below is a live example and the necessary code to replicate it:

const app = Vue.createApp({
  data: () => ({ display: true }),
  methods: {
    toggleText() {
      this.display = !this.display;
    }
  },
  template: `
  <div>
    <h1 v-if="display">Hello!</h1>
    <h1 v-else>Goodbye :(</h1>
    <button @click="toggleText()">Toggle</button>
  </div>
  `
}).mount('#content');

An element with a v-else directive must immediately follow an element with a v-if or v-else-if directive. Otherwise, the v-else element will always render, and Vue will log the below warning to the console:

[email protected]:1616 [Vue warn]: Template compilation error: v-else/v-else-if has no adjacent v-if or v-else-if.
3  |        <h1 v-if="display">Hello</h1>
4  |        <h1>World</h1>
5  |        <h1 v-else>Goodbye</h1>
   |        ^^^^^^^^^^^^^^^^^^^^^^^
6  |        <button @click="toggleText()">Toggle</button>
7  |      </div> 
  at <App>

Below is a live example of a v-else without an adjacent v-if. Notice that the "Goodbye" h1 renders regardless of the display value.

const app2 = Vue.createApp({
  data: () => ({ display: true }),
  methods: {
    toggleText() {
      this.display = !this.display;
    }
  },
  // BAD: the below template has a `v-else` that isn't adjacent to a `v-if`
  template: `
  <div>
    <h1 v-if="display">Hello</h1>
    <h1>World</h1>
    <h1 v-else>Goodbye</h1>
    <button @click="toggleText()">Toggle</button>
  </div>
  `
}).mount('#content2');

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