属性或方法“greet”未在实例上定义，但在渲染期间被引用

Question

Same time I got an another error, which is "Invalid handler for event "click"".

<template>
    
    <div id="example-2">
      <!-- `greet` is the name of a method defined below -->
      <button v-on:click="greet">Greet</button>
    </div>
    
    </template>
    
    <script>
    window.onload = function () {
    
    var example2 = new Vue({
      el: '#example-2',
      data: {
        name: 'Vue.js'
      },
      // creating method greet
      methods: {
        greet: function (event) {
          // `this` inside methods points to the Vue instance
          alert('Hello ' + this.name + '!')
          // `event` is the native DOM event
          if (event) {
            alert(event.target.tagName)
          }
        }
      }
    })
    
    }
    
    </script>

Answer 1

the template tag is hidden when the HTML loads so you get the error cannot find element or something like that. You can load it with javascript.

Vue.js does not use the built in template tag.

However if you using it over cdn try it like this

  <div id="example-2">
    <button v-on:click="greet">Greet</button>
  </div>

  <script>
    var example2 = new Vue({
      el: "#example-2",
      data: {
        name: "Vue.js",
      },
      methods: {
        greet: function(event) {
          alert("Hello " + this.name + "!");
          if (event) {
            alert(event.target.tagName);
          }
        },
      },
    });
  </script>

Answer 2

What you can simply do is remove the template tags

Here is the working code: https://jsfiddle.net/t49zxdov/2/

<div id="example-2">
      <!-- `greet` is the name of a method defined below -->
      <button v-on:click="greet">Greet</button>
    </div>
    

window.onload = function () {
    
        var example2 = new Vue({
      el: '#example-2',
      data: {
        name: 'Vue.js'
      },
      // creating method greet
      methods: {
        greet: function (event) {
          // `this` inside methods points to the Vue instance
          alert('Hello ' + this.name + '!')
          // `event` is the native DOM event
          if (event) {
            alert(event.target.tagName)
          }
        }
      }
    })
    
    }

Answer 3

You should separate your vue template and the vue instance. To do that,

create file, ex: example.vue copy this code

<template>
    <div id="example-2">
      <!-- `greet` is the name of a method defined below -->
      <button v-on:click="greet">Greet</button>
    </div>
</template>
<script>
  data() {
     return {
         name: 'Vue.js'
     }
  },
  methods: {
        greet: function (event) {
          // `this` inside methods points to the Vue instance
          alert('Hello ' + this.name + '!')
          // `event` is the native DOM event
          if (event) {
            alert(event.target.tagName)
          }
        }
      }
</script>

and create this file, ex: app.js

const app = new Vue({
    el: '#example-2', 
});

and then link your app.js to your index layout.

I hope you get my point. thanks