Vue - Snippets

Basics

• Data Option / Function
• Methods Option / Object
• Outputting Data mit
  • Interpolation {{}}
  • Bindings v-bind:property="myVal"
  • Methods
  • JavaScript Objects
• this

// create App
const app = Vue.createApp();
// mount a html region
// app.mount('cssSelector');
app.mount('#myId'); // Vue controls now this id in the DOM


const app = Vue.createApp({
  // DATA FUNCTION can hold key val pairs
  data() { //or data: function(){...}
    return{ // data always returns an object
      myVar: 'Learn Vue',// can store keys with vals of every type(bool, object, string...)
      myVar2: 'Master Vue<, 
      myHTML: '<h3>HTML Code</h3>', // use v-html to output html code
      myLink: 'https://viewjs.org'
    }; 
  }
  // METHODS OBJECT HOLDS FUNCTIONS
  methods: {
    outputGoal(){
      const randomNumber = Math.random();
      if (randomNumber < 0.5) {return 'Learn Vue';}
      else {return this.myVar2} // 'this' works because vue merges all data and methods in a global vue object
    }
  }
});

<div id="myId">
<h3>Interpolation</h3>
<p>{{ myVar }}</p> <!-- Interpolation outputs "Learn Vue" -->
<h3>Binding</h3>
<p>Use bindings to set attributes. I.e. set the href attribute. {{myLink}} wouldn't work inside of tags.</p>
<p>Learn more <a v-bind:href="myLink">about Vue</a></p>
<p>{{ outputGoal() }}</p><!-- functions or simple js expresseions like 1+1 work to -->
<p v-html="myHTML"></p>
</div>

Events

Beispiel

const app = Vue.createApp({
  data() {
    return {
      counter: 0,
    };
  },
  methods:{
    plus(n){ this.counter = this.counter + n },
    minus(n){ this.counter = this.counter - n },
    updateName(event){
      this.name = event.target.value
    }
  }
});

app.mount('#events');

<section id="events">
  <h2>Events in Action</h2>
  <p> We can use expression in v-on:click or use a function from our methods object</p>
  <!-- CLICK EVENT -->
  <button v-on:click="plus(5)">Add 5</button>
  <button v-on:click="minus(5)">Substract 5</button>
  <p>Result: {{ counter }}</p>
  <!-- INPUT EVENT -->
  <input type="text" v-on:input="updateName">
  <p>Hello {{ name }}</p>

</section>

$event

In Eventlistenern kann man automatisch auf das event Argument zugreifen, das der Browser automatisch mitliefert (siehe Beispiel oben). Wenn man allerdings selbst ein Argument übermittelt wird das Event Argument überschrieben. Man kann aber mit dem reservierten Argument $event trotzdem wieder auf das Event Objekt zugreifen:

    updateName(event, lastName){
      this.name = event.target.value + ' ' + lastName
    }

      <input type="text" v-on:input="updateName($event,'Schlegel')">
      <p>Hello {{ name }}</p>

Event Modifiers

Es gibt verschiedene Event Modifier z.B. um sich ein event.preventDefault() zu sparen. Event Modifiers werden mit einem '.' an das Event im HTML angehängt

v-on:submit.prevent

https://vuejs.org/v2/guide/events.html#Event-Modifiers

Click Modifiers

v-on:click.right
v-on:click.middle
...

Key Modifiers

//.enter means fire only if ENTER Key is pressed
v-on:keyup.enter="confirmInput" //possible is all ctrl, shift, page-down...

<!--also multiple v-on handlers are possible--<
<input type="text" v-on:input="updateName($event,'Schlegel')" v-on:keyup.enter="confirmName">
<p>Hello {{ confirmedName }}</p>

const app = Vue.createApp({
  data() {
    return {
      name: '',
      confirmedName: '',
    };
  },
  methods:{
    updateName(event, lastName){
      this.name = event.target.value + ' ' + lastName
    },
    confirmName(){
      this.confirmedName = this.name 
    }
  }
});
app.mount('#events');