Form Validation in a Vue 3 App with Vee-Validate 4 — Files and Integers

Form validation is an important part of any app.

In this article, we’ll look at how to use Vee-Validate 4 in our Vue 3 app for form validation.

ext

The ext validation rule checks that the file selected has one of the extensions listed.

For example, we can write:

<template>
  <Form @submit="onSubmit" v-slot="{ errors }">
    <Field name="field" type="file" rules="ext:jpg,png" />
    <span>{{ errors.field }}</span>
  </Form>
</template>
<script>
import { Form, Field, defineRule } from "vee-validate";
import * as rules from "@vee-validate/rules";

Object.keys(rules).forEach((rule) => {
  defineRule(rule, rules[rule]);
});

export default {
  components: {
    Form,
    Field,
  },
  methods: {
    onSubmit(values) {
      alert(JSON.stringify(values, null, 2));
    },
  },
};
</script>

Then the selected file must either have the jpg or png extensions.

We can add any number of extensions to the list.

Also, we can write:

<template>
  <Form @submit="onSubmit" v-slot="{ errors }">
    <Field name="field" type="file" :rules="validations" />
    <span>{{ errors.field }}</span>
  </Form>
</template>
<script>
import { Form, Field, defineRule } from "vee-validate";
import * as rules from "@vee-validate/rules";

Object.keys(rules).forEach((rule) => {
  defineRule(rule, rules[rule]);
});

export default {
  components: {
    Form,
    Field,
  },
  data() {
    return {
      validations: { ext: ["jpg", "png"] },
    };
  },
  methods: {
    onSubmit(values) {
      alert(JSON.stringify(values, null, 2));
    },
  },
};
</script>

We have the extensions in an array.

image

The image rule lets validate that the selected file has a MIME-type that starts with image/ .

For instance, we can write:

<template>
  <Form @submit="onSubmit" v-slot="{ errors }">
    <Field name="field" type="file" rules="image" />
    <span>{{ errors.field }}</span>
  </Form>
</template>
<script>
import { Form, Field, defineRule } from "vee-validate";
import * as rules from "@vee-validate/rules";

Object.keys(rules).forEach((rule) => {
  defineRule(rule, rules[rule]);
});

export default {
  components: {
    Form,
    Field,
  },
  methods: {
    onSubmit(values) {
      alert(JSON.stringify(values, null, 2));
    },
  },
};
</script>

We set the rules prop to 'image' to restrict the selected file to be an image.

Also, we can write:

<template>
  <Form @submit="onSubmit" v-slot="{ errors }">
    <Field name="field" type="file" :rules="validations" />
    <span>{{ errors.field }}</span>
  </Form>
</template>

<script>
import { Form, Field, defineRule } from "vee-validate";
import * as rules from "@vee-validate/rules";

Object.keys(rules).forEach((rule) => {
  defineRule(rule, rules[rule]);
});

export default {
  components: {
    Form,
    Field,
  },
  data() {
    return {
      validations: { image: true },
    };
  },
  methods: {
    onSubmit(values) {
      alert(JSON.stringify(values, null, 2));
    },
  },
};
</script>

to do the same thing.

integer

The integer rule lets us validate that the inputted value must be an integer.

For instance, we can write:

<template>
  <Form @submit="onSubmit" v-slot="{ errors }">
    <Field name="field" rules="integer" />
    <span>{{ errors.field }}</span>
  </Form>
</template>

<script>
import { Form, Field, defineRule } from "vee-validate";
import * as rules from "@vee-validate/rules";

Object.keys(rules).forEach((rule) => {
  defineRule(rule, rules[rule]);
});

export default {
  components: {
    Form,
    Field,
  },
  methods: {
    onSubmit(values) {
      alert(JSON.stringify(values, null, 2));
    },
  },
};
</script>

to add the integer rule to the rules prop.

Also, we can write:

<template>
  <Form @submit="onSubmit" v-slot="{ errors }">
    <Field name="field" :rules="validations" />
    <span>{{ errors.field }}</span>
  </Form>
</template>

<script>
import { Form, Field, defineRule } from "vee-validate";
import * as rules from "@vee-validate/rules";

Object.keys(rules).forEach((rule) => {
  defineRule(rule, rules[rule]);
});

export default {
  components: {
    Form,
    Field,
  },
  data() {
    return {
      validations: { integer: true },
    };
  },
  methods: {
    onSubmit(values) {
      alert(JSON.stringify(values, null, 2));
    },
  },
};
</script>

to do the same thing.

Conclusion

We can validate that the selected file has the given extension or that it’s an image with Vee-Validate 4 in our Vue 3 app.

Also, we can validate that what the user entered is an integer.