React-native Validation using validate.js

Validate.js

	import validation from 'validate.js'

	export default function validate(fieldName, value) {
	    var constraints = {
		email: {
		    presence: true,
		    format: {
		        pattern: /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/,
		        message: 'Invalid email id',
		    }
		},
		password: {
		    presence: true,
		    length: {
		        minimum: 4,
		        message: 'Invalid Password',
		    }
		},
		confirmPassword: {
		    presence: true,
		    equality: 'password'
		},
		phoneNo: {
		    presence: true,
		    format: {
		        pattern: "^[0-9]{10}$",
		        message: 'Invalid phone number',
		    },
		},
	    };

	    var formValues = {}
	    formValues[fieldName] = value

	    var formFields = {}
	    formFields[fieldName] = constraints[fieldName]


	    const result = validation(formValues, formFields)

	    if (result) {
		return result[fieldName][0]
	    }
	    return null
	}