Field

Settings up field validation are straightforward, and all thing begins from Field function followed by the type of field you want to validate.

import { Field } from "v4f"; // ES6

Field().string(); // Chain your rules after this

import { Field } from "v4f"; // ES6

Field().number(); // Chain your rules after this

import { Field } from "v4f"; // ES6

Field().boolean(); // Chain your rules after this

import { Field } from "v4f"; // ES6

Field().array(); // Chain your rules after this

import { Field } from "v4f"; // ES6

Field().object(); // Chain your rules after this

import { Field } from "v4f"; // ES6

Field().any(); // Chain your rules after this

Chaining Rules

To build the field validation, we use a model called chaining, Essentially means that you make each validation rule after one another, This creates a smooth typing experience.

const username = Field()
    .string()
    .min(6)
    .max(10)
    .first("Fa")
    .required();

Validation

To validate data, call the function validate with data as an argument.

const isValid = username.validate("baduser");

// isValid equals false

Not Modifier

Sometimes you might want the inverse of a rule. For example, you might want to check that something isn't empty, here where do modifiers come in action.

Field()
    .string()
    .not.empty()
    .validate(""); // false

Custom Message

the fundamental strength of v4f is that you can define a custom message for every rule.

const username = Field()
    .string({
        message: "Username field must be string"
    })
    .min(6, {
        message: "Username field length must be grater that 6"
    })
    .max(10, {
        message: "Username field length must be less than 10"
    })
    .first("Fa", {
        message: "Username field must start with Fa"
    })
    .required({
        message: "Username field is required"
    });

// to get the message instead of boolean, you must turn on the verbose option to true.

const isValid = username.validate("baduser", { verbose: true });
/**
 * is valid contain "Username field must start with Fa"
 * if we pass valid data isValid will contain true
 */
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