Vue - Snippets

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Vue.js
Vue - Basic Concepts
Vue CLI
Vue - Components

Snippets

Starter

const app = Vue.createApp({
  data(){
    return{
    }
  },
  methods:{
  },
  computed:{
  },
  watch:{
  }
});
app.mount('#assignment');

Using this in a submethod i.e. Timer

watch:{
  // it is allowed to watch computed properties
  result(value){
    const that = this;
    setTimeout(function(){
      console.log("timeout");
      that.counter = 0;
      return 0;
    },3000); 
  }
}

Toggle Classes

//...
data(){ return { boxSelected: false } },
methods:{ toggleBox(){ this.boxSelected = !this.boxSelected; } }
//...

<div @click="selectBox()" class="box" :class="{ active : boxSelected }"></div>

Add and remove items to / from a list

const app = Vue.createApp({
  data() {
    return { 
      enteredGoalValue: '',
      goals: []
     };
  },
  methods: {
    addGoal() {
      this.goals.push(this.enteredGoalValue);
      this.enteredGoalValue = '';
    },
    removeGoal(i){
      console.log("removeGoal " + i)
      this.goals.splice(i,1); // splice 1 item at index i 
    }
  }
});
app.mount('#user-goals');

   <section id="user-goals">
      <h2>My course goals</h2>
      <input type="text" v-model="enteredGoalValue" />
      <button @click="addGoal">Add Goal</button>
      <p v-if="goals.length === 0">No goals have been added yet - please start adding some!</p>
      <ul v-else> 
        <li v-for="(goal, i) in goals" @click="removeGoal(i)" :key="[myID]">#{{i}} {{goal}}</li> // use a unique id for key attribute
      </ul>
    </section>

Components

Component Todos

Mit CLI

• myComponent.vue Datei erstellen
• In main.js Import und component Funktion
• In App.vue Import
• In myComponent.vue props, emits festlegen
• In App.vue emits als v-on nutzen
• In App.vue props als Argumente übergeben

Utilities / nützliche Funktionen

Normale JavaScript Funktionen die oft nützlich im Zusammenhang mit Vue sind.

Arrays

Gegeben ist ein Array items in der Art

[{id: 1, name: Anton, isFavourite: true}, {id: 2, name: Berta},...]

// add to end of array
this.friends.push(newFriend)

// find in array and change prop
const identifiedItem = this.items.find(
  (item) => item.id === searchId // the same as function(friend){return friend.id...}
)
// filter(callback) - callback is executed on every array (array item) first item match is returned
identifiedItem.isFavourite = !identifiedItem.isFavourite
// identifiedItem is a proxy connected to the original items array.
// thus why we can modify identifiedItems and items will be altered too

// delete item from array via id
deleteItem(id){
  this.items = this.items.filter( item => item.id !== sarchId)
  // filter( filterFunction ) uses filterFunction for every item in items.
  // If filterFunction returns true the item is kept. item.id !== id returns true for every
  // item which has NOT the id
}