Category: JavaScript

Sometimes, we want to preview an image before it is uploaded with Vue.js.

In this article, we’ll look at how to preview an image before it is uploaded with Vue.js.

How to preview an image before it is uploaded with Vue.js?

To preview an image before it is uploaded with Vue.js, we can convert the selected image file into a URL and then set the URL as the value of the img element src attribute.

For instance, we write

<template>
  <div id="app">
    <input type="file" @change="onFileChange" />

    <div>
      <img v-if="url" :src="url" />
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      url: null,
    };
  },
  methods: {
    onFileChange(e) {
      const [file] = e.target.files;
      this.url = URL.createObjectURL(file);
    },
  },
};
</script>

to add a file input and an img element for showing the preview.

Then we add the onFileChange method which is called when we select a file since we have

@change="onFileChange"

Then we get the selected file in the method with e.target.files.

And then we convert the image file to a URL with URL.createObjectURL and assign it to this.url.

Then we set :src to url in the img element to show the selected image file.

Conclusion

To preview an image before it is uploaded with Vue.js, we can convert the selected image file into a URL and then set the URL as the value of the img element src attribute.

Sometimes, we want to convert string to DOM elements in Vue.js.

In this article, we’ll look at how to convert string to DOM elements in Vue.js.

How to convert string to DOM elements in Vue.js?

To convert string to DOM elements in Vue.js, we can use the v-html directive.

For instance, we write

<template>
  <div>
    <div v-html="yourVariable"></div>
  </div>
</template>

to render the yourVariable HTML string into DOM elements with the v-html directive.

Conclusion

To convert string to DOM elements in Vue.js, we can use the v-html directive.

Sometimes, we want to disable button until all validation rules are true with Vuetify and Vue.js.

In this article, we’ll look at how to disable button until all validation rules are true with Vuetify and Vue.js.

How to disable button until all validation rules are true with Vuetify and Vue.js?

To disable button until all validation rules are true with Vuetify and Vue.js, we can bind a reactive property to the form validation result value with v-model on v-form.

And then we can use that to conditionally disable the button.

For instance, we write

<template>
  <div>
    <v-form v-model="isFormValid"> ... </v-form>

    <v-btn :disabled="!isFormValid">Add</v-btn>
  </div>
</template>

to bind the isFormValid reactive property to the form validation with v-form‘s v-model directive.

Then we disable the v-btn when isFormValid is false with

:disabled="!isFormValid"

Conclusion

To disable button until all validation rules are true with Vuetify and Vue.js, we can bind a reactive property to the form validation result value with v-model on v-form.

And then we can use that to conditionally disable the button.

Sometimes, we want to check if Vue.js is in development mode.

In this article, we’ll look at how to check if Vue.js is in development mode.

How to check if Vue.js is in development mode?

To check if Vue.js is in development mode, we can check the value of process.env.NODE_ENV.

For instance, we write

process.env.NODE_ENV === "development";

to check if process.env.NODE_ENV is 'development' to see if the app is running in development mode.

Conclusion

To check if Vue.js is in development mode, we can check the value of process.env.NODE_ENV.

Sometimes, we want to fix the ‘Unknown custom element: v-app – did you register the component correctly?’ error with Vuetify and Vue.js.

In this article, we’ll look at how to fix the ‘Unknown custom element: v-app – did you register the component correctly?’ error with Vuetify and Vue.js.

How to fix the ‘Unknown custom element: v-app – did you register the component correctly?’ error with Vuetify and Vue.js?

To fix the ‘Unknown custom element: v-app – did you register the component correctly?’ error with Vuetify and Vue.js, we should call Vue.use before creating the Vue instance.

For instance, we write

Vue.use(Vuetify);

new Vue({
  el: "#app",
  components: { App },
  template: "<App/>",
});

We call Vue.use with Vuetify to register the Vuetify plugin globally.

And then we create a new Vue instance.

Then we can use v-app in our components.

Conclusion

To fix the ‘Unknown custom element: v-app – did you register the component correctly?’ error with Vuetify and Vue.js, we should call Vue.use before creating the Vue instance.