A tiny JavaScript library for form validation.

Ok.js is a utility library to validate forms with more than what HTML5 offers you. Features include customized messages and validator chaining.

Documentation

Install the package:

npm install okjs --save

Ok.js offers two different APIs to interact with it:

• The data-attribute API works via HTML data-attributes and works well without any frontend framework.
• The composition API uses a more functional approach and is useful when combined with a frontend framework such as Vue or React.

The two offer the same functionality, but depending on your use-case, one may be preferable.

The data-attribute API works well when working directly with HTML that is enhanced by JS.

import { Ok } from "okjs";

/**
 * Create Ok instance with custom validators.
 */
const ok = new Ok({
	/**
	 * A validator with the name 'nameFirst'.
	 */
	nameFirst: {
		msg: "Only 'Dave' allowed",
		/**
		 * Validation passes if the element value is "Dave".
		 */
		fn: (element) => element.value === "Dave",
	},
	emailDe: {
		msg: (element) =>
			`Please input your .de email (You entered '${element.value}')`,
		fn: (element) => element.value.endsWith(".de"),
	},
});

/**
 * Bind validation event handlers to inputs.
 */
document.querySelectorAll("[data-ok]").forEach((el) => {
	el.addEventListener("input", (e) => ok.validate(e.target));
});

The validator which will be used is defined in the DOM via data-ok data-attributes:

<form>
	<label for="demo1_1">First Name (only "Dave" allowed)</label>
	<input id="demo1_1" type="text" required data-ok="nameFirst" />

	<label for="demo1_2">Last Name (not validated, anything goes)</label>
	<input id="demo1_2" type="text" required />

	<label for="demo1_3">Email address (only ".de" allowed)</label>
	<input id="demo1_3" type="email" required data-ok="emailDe" />

	<input type="submit" />
</form>

The value defined in data-ok is the key of the validator dictionary object provided in the JavaScript Ok.js constructor parameter. If the given function evaluates to false, the input will be marked as invalid, and the message will be shown.

The composition API works well if you already use a frontend framework like React or Vue, and do not want to use data attributes for logic.

Example using React:

import { validate } from "okjs";

/**
 * A validator with the name 'nameFirst'.
 */
const nameFirst = {
	msg: "Only 'Dave' allowed",
	fn: (element) => element.value === "Dave",
};

const emailDe = {
	msg: (element) =>
		`Please input your .de email (You entered '${element.value}')`,
	fn: (element) => element.value.endsWith(".de"),
};

const SomeComponent = () => {
	const handleNameChange = (e) => {
		/**
		 * Trigger validation using the 'nameFirst' validator.
		 */
		validate(e.target, [nameFirst]);
	};
	const handleEmailChange = (e) => {
		validate(e.target, [emailDe]);
	};

	return (
		<form>
			<label htmlFor="demo2_1">First Name (Only 'Dave' allowed)</label>
			<input id="demo2_1" type="text" onChange={handleNameChange} />

			<label htmlFor="demo2_2">
				Last Name (not validated, anything goes)
			</label>
			<input id="demo2_2" type="text" required />

			<label htmlFor="demo2_3">Email address (only ".de" allowed)</label>
			<input
				id="demo2_3"
				type="email"
				required
				onChange={handleEmailChange}
			/>

			<input type="submit" />
		</form>
	);
};

Multiple validators can be used for a single element in a given order by chaining them. To chain multiple validators, add a comma between their names in the data-attribute. When using chaining, the field will only be considered valid if all validators succeed. Once a validator marks the field as invalid, all further validators are skipped.

<label for="demo2_1">Email ID (all caps and ending in .de)</label>
<input id="demo2_1" type="email" required data-ok="nameCaps,emailDe" />

In the composition API, the additional validators can be specified when calling validate:

validate(e.target, [nameCaps, emailDe]);

While Ok.js itself does not localize validation messages, the validation message function can call an existing localization function:

import { localize } from "./some-localization-tool";

const nameFirst = {
	msg: () => localize("validation.error.daveOnly"),
	fn: (element) => element.value === "Dave",
};

Due to the way input elements with type radio work, validation is not straightforward. A single radio button only fires its change/input event when itself is changed, not if it becomes inactive due to another radiobutton being selected. A workaround is using an enclosing fieldset and listening to the events of that.

Ok.js should work in all browsers that support the following:

• https://caniuse.com/form-validation
• https://caniuse.com/mdn-api_htmlinputelement_setcustomvalidity