Unterschiede

Hier werden die Unterschiede zwischen zwei Versionen angezeigt.

--- en:modul:m291:learningunits:lu05:theorie:04 [2025/01/27 12:33] – vdemir
+++ en:modul:m291:learningunits:lu05:theorie:04 [2025/03/14 13:46] (aktuell) – vdemir
@@ Zeile 1: / Zeile 1: @@
-====== LU05d - v-if - TBD ======
+====== LU05d - v-show ======
 ===== Learning ojectives =====
-  - I can explain what function v-if directives fulfil within the DOM.
+  - I can explain what directive v-show fulfil within the DOM.
-  - I can name the three v-if variants that are possible in principle.
+  - I can prove the visibility of objects using v-show.
-  - I can apply v-if to specific examples.
+  - I can use the v-show directive.
-===== Sources =====
+====== Sources ======
-  * [[https://www.w3schools.com/vue/vue_v-if.php | W3School - v-if]]
+  * [[https://www.w3schools.com/vue/vue_v-show.php|W3School | W3School | Conditional Rendering - v-show]]
-  * [[https://vuejs.org/guide/essentials/conditional.html | Vue.org - v-if ]]
+  * [[https://vuejs.org/guide/essentials/conditional.html#v-show | Vuejs.org | Conditional Rendering - v-show]]
 ===== Introduction ====
-The v-if directive in Vue.js is used to conditionally render elements in the DOM. If the condition provided in the //v-if// evaluates to true, the element is rendered; otherwise, it is removed from the DOM entirely. This makes v-if a powerful tool for controlling the visibility of elements based on dynamic data.
+The v-show directive in Vue.js is used to conditionally display elements based on a boolean expression. //Unlike v-if, which completely removes elements from the DOM when the condition is false//, v-show toggles the CSS display property, keeping the element in the DOM but hiding it visually. This makes v-show more efficient when elements need to be frequently shown or hidden without re-rendering. It is best suited for UI toggles, such as modals, dropdowns, or tooltips.
+The syntax is simple: isVisible controls the visibility of the element dynamically
+  <div v-show="isVisible">Content</div>
+===== Example =====
+  <template>
+    <div>
+      <button @click="isVisible = !isVisible">
+        Toggle Message
+      </button>
+      <p v-show="isVisible">Hello, Vue.js!</p>
+    </div>
+  </template>
-  <div id="app">
-    <button @click="toggleMessage">Toggle Message</button>
-    <p v-if="isVisible">Hello, Vue.js!</p>
-  </div>
   <script>
-    new Vue({
+    export default {
-      el: '#app',
+      data() {
-      data: {
+        return {
-        isVisible: true
+          isVisible: true
-      },
+        };
-      methods: {
-        toggleMessage() { this.isVisible = !this.isVisible;
       }
-    }
+    };
-    });
   </script>
-In this example above, the paragraph element (<p>) is conditionally displayed based on the value of the //isVisible// data property. Clicking the button toggles the message's visibility.
+**Explanation:**
+  * The v-show="isVisible" directive controls the visibility of the <p> element.
+  * Clicking the button toggles isVisible between true and false.
+  * Instead of removing the element from the DOM, Vue modifies its display property.
-===== Variants =====
+===== v-if VS v-show =====
-There are basically three variants of //v-if//:
+Both, v-if and v-show are conditional rendering, but unlike v-if, the v-show directive **only** make the object of concern **invisible**, for it is yet hidden part of the HTML-DOM.
-  - v-if
-  - v-else-of
-  - v-else
-==== 1. v-if ====
+===== Demonstration =====
-  * Used to conditionally render an element based on whether the condition evaluates to //true//.
-  * If the condition is //false//, the element is completely removed from the DOM.
-**Example:**
+[[https://www.w3schools.com/vue/tryit.php?filename=tryvue_v-show_div2 | v-show VS v-if]]
-  <p v-if="isVisible">This is visible when isVisible is true.</p>
-==== 2. v-else-if ====
-  * Used to create an additional condition in conjunction with //v-if//.
-  * orks like an //else-if// statement in programming, allowing multiple conditions to be checked.
-  <p v-if="condition === 'A'">Condition A is true.</p>
+  * **v-show:** Hides only an object, it is still accessible for fold-in or fold-out
-  <p v-else-if="condition === 'B'">Condition B is true.</p>
+  * **v-if:** The object of concern is no longer existing, as it was destroyed from the HTML-DOM.
-==== 3. v-else ====
-  * Provides a fallback for when none of the //v-if// or //v-else-if// conditions are met.
-  * It does not accept any condition and must directly follow //v-if// or //v-else-if//.
-  <p v-if="condition === 'A'">Condition A is true.</p>
+^Feature	^v-if	^v-show ^
-  <p v-else-if="condition === 'B'">Condition B is true.</p>
+| DOM Behavior | Completely adds/removes elements from the DOM | Only toggles the display property (keeps elements in the DOM) |
-  <p v-else>Neither condition A nor B is true.</p>
+| Performance | Better for infrequent changes (expensive re-rendering) | Better for frequent toggling (faster updates) |
+| Usage Case | When elements are rarely shown/hidden | When elements need to be toggled frequently |
-===== Additional Material =====
-{{:en:modul:m291:learningunits:lu05:theorie:vuejs_tutorial_10_v-if_v-else_v-else-if_conditional_rendering.mp4 | Youtube-Tutorial: conditional rendering}}
 ===== Vocabulary =====
 ^ English ^ German ^
-| to render | ausführen, wiedergeben |
+| conditionally | bedingt |
-| conjunction | verbindung |
+| to fold in/out | einklppen/ausklappen |
 ----
 [[https://creativecommons.org/licenses/by-nc-sa/4.0/|{{https://i.creativecommons.org/l/by-nc-sa/4.0/88x31.png}}]] Volkan Demir