What is the difference between v-show and v-if directives?

Introduction to v-show and v-if directives

The v-show and v-if directives in Vue.js are both used to conditionally render elements in the DOM, but they have different behavior and use cases.

V-show

• The v-show directive toggles the CSS display property of the element based on the truthiness of the expression provided.
• When the expression evaluates to true, the element is displayed (with display: block), and when it evaluates to false, the element is hidden (with display: none).
• The element remains in the DOM at all times, even when hidden, so it incurs a small performance overhead.
• v-show is useful when you want to toggle the visibility of an element frequently, such as in a tabbed interface or a dropdown menu.

  <template>
    <div>
      <button @click="toggleVisibility">Toggle</button>
      <div v-show="isVisible">This div is toggled with v-show</div>
    </div>
  </template>
  
  <script>
  export default {
    data() {
      return {
        isVisible: true
      };
    },
    methods: {
      toggleVisibility() {
        this.isVisible = !this.isVisible;
      }
    }
  };
  </script>
  

V-if

• The v-if directive removes or adds the element to/from the DOM based on the truthiness of the expression provided.
• When the expression evaluates to true, the element is added to the DOM; when it evaluates to false, the element is removed from the DOM.
• v-if has higher initial rendering overhead compared to v-show because it must create or destroy the element in the DOM each time the condition changes.
• v-if is useful when you want to conditionally render an element that may not be needed initially or may not be needed frequently.

  <template>
    <div>
      <button @click="toggleVisibility">Toggle</button>
      <div v-if="isVisible">This div is toggled with v-if</div>
    </div>
  </template>
  
  <script>
  export default {
    data() {
      return {
        isVisible: true
      };
    },
    methods: {
      toggleVisibility() {
        this.isVisible = !this.isVisible;
      }
    }
  };
  </script>
  

Key differences between v-show and v-if

• Performance: V-show has better performance when toggling visibility frequently because it simply changes the CSS display property, while v-if has a higher initial rendering cost because it creates or destroys the element in the DOM.
• Initial Rendering: V-show elements are always rendered initially in the DOM, while v-if elements are only rendered when the condition is true.
• DOM Manipulation: V-show toggles the visibility of an existing element, while v-if adds or removes the element from the DOM based on the condition.

Summary

V-show toggles the visibility of an element by toggling its CSS display property, while v-if conditionally renders or removes the element from the DOM. Use v-show for elements that need to be toggled frequently but always remain in the DOM, and use v-if for elements that may not always be needed or don't need to be in the DOM until certain conditions are met.