Vue.js Conditional Rendering and V-if vs V-show

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Vue.js Conditional Rendering

v-if and v-show directives are used to conditionally render a block in Vue.js.

v-if

In vue.js, the directive v-if is used to conditionally render a block. The block will only be rendered if the directive's expression returns a truthy value.

Example :

<script setup>
import { ref } from 'vue'

const show = ref(true)
</script>

<template>
  <button @click="show = !show">toggle</button>
    <h1 v-if="show">Vue.js</h1>
</template>

You can use the v-else directive to indicate an "else block" for v-if. If the v-if directive expression does not return true, v-else block is rendered.

<script setup>
import { ref } from 'vue'

const show = ref(true)
</script>

<template>
  <button @click="show = !show">toggle</button>
    <h1 v-if="awesome"> v-if directive </h1>
    <h1 v-else> v-else directive </h1>
</template>

v-else-if

The v-else-if, serves as an "else if block" for v-if. It can also be chained multiple times. When v-if and v-else-if do not evaluate to true, the v-else directive is triggered.

 <p v-if="currentState === 0">State 0: Message 1</p>
    <p v-else-if="currentState === 1">State 1: Message 2</p>
    <p v-else-if="currentState === 2">State 2: Message 3</p>
    <p v-else>State 3: Message 4</p>

v-show

When we want to display an item conditionally, we can use the v-show directive as another option.

<h1 v-show="ok">Ok!</h1>

The difference is that an element with a v-show is always rendered and remains in the DOM. v-show changes the CSS display property to show or hide the element. v-show doesn't work with v-else

v-if vs. v-show

v-if is "real" conditional rendering because it ensures that event listeners and child components inside the conditional block are properly destroyed and re-created during toggles.

v-if : if the condition is false on initial render, it will not do anything - the conditional block won't be rendered until the condition becomes true for the first time.

v-show is always rendered and remains in the DOM. v-show changes the CSS display property to show or hide the element. v-show doesn't work with v-else

v-if has higher toggle costs while v-show has higher initial render costs. prefer v-show if you need to toggle something very often, and prefer v-if if the condition is unlikely to change at runtime.

Conclusion

In this article, we examined the features and differences of v-if and v-show directives. Understanding these distinctions is essential for optimizing rendering performance and managing element visibility in your Vue.js applications.

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