JS Form Validator is a simple form data validation library for JavaScript. It provides a set of base rules for checking the type and value of various inputs, and allows you to define custom rules as well.
To install JS Form Validator, use one of the following package managers:
npm install --save js-formdata-validator
pnpm add js-formdata-validator
// nuxt.config.js
// Add transpile
build: {
transpile: [/js-formdata-validator/],
},
To use JS Form Validator, import the Validator class and create a new instance, passing in an object with the following properties:
- formData: An object containing the form data to be validated.
- rules: An object specifying the validation rules for each field in the form data. (rules is not required to be pass as an parameter here) Here's an example of how to use JS Form Validator to validate a form with a required name field:
import { Validator } from "js-formdata-validator";
const formData = {
name: null,
deep: {
neested: {
object: {
value: null
}
}
},
arrayObject: [
{
objectName: "object a name"
},
{
objectName: null
},
{
objectName: "object c name"
},
]
};
const validator = new Validator({
formData: formData,
rules: {
name: ["required"],
"deep.nested.object.value": ["required"],
"arrayObject.*.objectName": ["required"]
},
});
// Validate the form data
await validator.validate();
// Check if the validation failed
if (validator.fail()) {
// Get the validation error messages
const error = validator.getErrorBag();
console.log(error); // Output: {name: ["The field is required."], "deep.nested.object.value": ["The field is required."], "arrayObject.1.objectName": ["The field is required."]}
}
JS Form Validator provides the following base rules for validating form data:
| Validation Type | Description |
|---|---|
| required | Checks if the value is undefined, an empty string, or null. |
| array | Checks if the value is an instance of the Array class. |
| integer | Checks if the value is an integer using the Number.isInteger() method. |
| numeric | Checks if the value is an instance of the Number class. |
| string | Checks if the value is a string. |
| boolean | Checks if the value is a boolean. |
| allowed | Checks if the value is included in a list of allowed values passed as arguments to the function. |
| image | Checks if the value is an instance of the File class, and also checks if the file's MIME type starts with "image/". |
| size | Checks if the value is an instance of the File class, and also checks if the file's size is within a specified range. |
| Checks if the value is an email value. | |
| min | Checks if the value is more than min value. |
| max | Checks if the value is below the max value. |
| accepted | Checks if the value is accepted ("yes", "on", 1, true). |
| between | Checks if the value is between 2 arg (between:1,3). |
| declined | Checks if the value is declined ("no", "off", 0, false). |
| ipv4 | Checks if the value is ipv4. |
| ipv6 | Checks if the value is ipv6. |
| date | Checks if the value type is date. |
JS Form Validator provides extendable custom rule to be runs alongside base rules, heres the code example:
const formData = {
age: 25,
};
const validator = new Validator({
formData: formData,
rules: {
age: ["custom"],
},
}).mergeCustomRules({
custom(value) {
if (value === 25) {
return "Test Error";
}
},
});
// Validate the form data
await validator.validate();
// Check if the validation failed
if (validator.fail()) {
// Get the validation error messages
const error = validator.getErrorBag();
console.log(error);
}
We can also parse parameters to the custom rules
const formData = {
age: 25
};
const validator = new Validator({
formData: formData,
rules: {
age: ["ageBetween:26,50"]
},
})
validator.mergeCustomRules({
ageBetween(value, paramA, paramB) {
// paramA will be 26
// paramB will be 50
if (value < paramA || value > paramB) {
return `Age must be between ${paramA} - ${paramB}`;
}
},
});
Or set anonymous function inside the array rules
const formData = {
age: 25
};
const validator = new Validator({
formData: formData,
rules: {
age: [
(value) {
const min = 26
const max = 50
if (value < min || value > max) {
return `Age must be between ${min} - ${max}`;
}
}
]
},
})
It can also use async / await syntax to fetch data and wait it to be fetched from some external source
const formData = {
age: 25
};
const validator = new Validator({
formData: formData,
rules: {
age: [
async (value) {
const response = await fetch('/path/to/your/api');
const { min, max } = response.json();
if (value < min || value > max) {
return `Age must be between ${min} - ${max}`;
}
}
]
},
})