Vue is not defined

20
votes

I am trying to build a demo app with Vue.js. What I am getting is an odd error that Vue is not defined.

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Vue JS Intro</title>
</head>
<body>
    <div id="demo">
        <p>{{message}}</p>
        <input v-model="message">
    </div>

    <script type="JavaScript" src="https://cdnjs.cloudflare.com/ajax/libs/vue/1.0.18/vue.min.js"></script>

    <script>
        var demo = new Vue({
            el: '#demo',
            data: {
                message: 'Hello Vue.js!'
            }
        })
    </script>
</body>
</html>

What did I miss here? This is not a CDN issue as I also downloaded the library from the official website, used it and got the same result

index.html:15 Uncaught ReferenceError: Vue is not defined

8
javascripthtmlvue.js

8 Answers

33
votes

jsBin demo

  1. You missed the order, first goes: 

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/1.0.18/vue.min.js"></script>

and then: 

<script>
    var demo = new Vue({
        el: '#demo',
        data: {
            message: 'Hello Vue.js!'
        }
    });
</script>
  1. And type="JavaScript" should be type="text/javascript" (or rather nothing at all)
3
votes

try to fix type="JavaScript" to type="text/javascript" in you vue.js srcipt tag, or just remove it. Modern browsers will take script tag as javascript as default.

3
votes

Sometimes the problem may be if you import that like this:

const Vue = window.vue;

this may overwrite the original Vue reference.

1
votes

I got this error but as undefined due to the way I included js files

Initailly i had 

<script src="~/vue/blade-account-update-credit-card-vue.js" asp-append-version="true"></script>
<script src="~/lib/vue/vue_v2.5.16.js"></script>

in the end of my .cshtml page GOT Error Vue not Defined but later I changed it to

<script src="~/lib/vue/vue_v2.5.16.js"></script> 
<script src="~/vue/blade-account-update-credit-card-vue.js" asp-append-version="true"></script>

and magically it worked. So i assume that vue js needs to be loaded on top of the .vue

1
votes

I found two main problems with that implementation. First, when you import the vue.js script you use type="JavaScript" as content-type which is wrong. You should remove this type parameter because by default script tags have text/javascript as default content-type. Or, just replace the type parameter with the correct content-type which is type="text/javascript".

The second problem is that your script is embedded in the same HTML file means that it may be triggered first and probably the vue.js file was not loaded yet. You can fix this using a jQuery snippet $(function(){ /* ... */ }); or adding a javascript function as shown in this example: 

// Verifies if the document is ready
function ready(f) {
  /in/.test(document.readyState) ? setTimeout('ready(' + f + ')', 9) : f();
}

ready(function() {
  var demo = new Vue({
    el: '#demo',
    data: {
      message: 'Hello Vue.js!'
    }
  })
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="demo">
  <p>{{message}}</p>
  <input v-model="message">
</div>
0
votes

I needed to add the script below to index.html inside the HEAD tag. 

<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>

But in your case, since you don't have index.html, just add it to your HEAD tag instead.

So it's like:

<!doctype html>
<html>
<head>
   <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
...
</body>
</html>
0
votes

I had the same problem and for a strange reason, the js that contains the Vue, has a defer inside the script definition:

<script src="js/app.js" defer></script>

That caused the script loads asynchronously than the other js files.

After I remove the defer tag, the problem was solved.

-1
votes

just put text/javascript in your script tag which you use for cdn

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js" type="text/javascript"></script>