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Modern, simple, lightweight (~5kb gzip) form validation library written in Typescript, with no dependencies (no JQuery!). Support a wide range of predefined rules, async, files, dates validation, custom error messages and styles, localization. Support writing custom rules and plugins.

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Modern, simple, lightweight (~5kb gzip) form validation library written in Typescript, with no dependencies (no JQuery!). Support a wide range of predefined rules, async, files, dates validation, custom error messages and styles, localization. Supporting writing custom rules and plugins.

Why JustValidate?

It's a right choice for you, if you have a site, a landing page without React, JQuery etc. and you want to quick, simple and powerful solution for validating your form.

Features

  • small size and zero dependencies
  • no need to change your HTML
  • a wide range of pre-defined rules
  • custom rules
  • support plugins
  • custom styles and css classes for invalid fields and error messages
  • custom messages
  • showing tooltips as error messages
  • custom places for the error labels
  • localization (defining error messages for different languages)
  • user-friendly setup: console warning messages if something incorrect
  • written in Typescript and good test coverage

Installation

npm

npm install just-validate --save

yarn

yarn add just-validate

And then use it as an imported module:

import JustValidate from 'just-validate';

const validate = new JustValidate('#form');

Or if you don't use module bundlers, just include JustValidate script on your page from CDN and call it as window.JustValidate:

<script src="https://unpkg.com/just-validate@latest/dist/just-validate.production.min.js"></script>
<body>
  <script>
    const validate = new window.JustValidate('#form');
  </script>
</body>

Predefined rules

There are plenty of rules which you could use out of the box:

  • required, non-empty fields
  • valid email address
  • min/max text length
  • valid number
  • min/max number
  • valid password
  • valid strong password
  • check for the custom regexp
  • min/max count of uploaded files
  • min/max size, types, extensions, names of uploaded files
  • format date, check for isAfter/isBefore dates

Quick start

Let's say we have a basic HTML layout:

<form action="#" id="form" autocomplete="off">
  <label for="name">Enter your name</label>
  <input
    type="text"
    class="form__input form-control"
    placeholder="Enter your name"
    autocomplete="off"
    name="name"
    id="name"
  />
  <label for="email">Enter your email</label>
  <input
    type="email"
    class="form__input form-control"
    placeholder="Enter your email"
    autocomplete="off"
    name="email"
    id="email"
  />
  <button class="btn btn-primary" id="submit-btn">Submit</button>
</form>

Next, let's add JustValidate to our layout and define some simple rules.

First, we should create the instance new JustValidate('#form') by passing a form selector, or the element as an argument.

Second, we call .addField() with a field selector as the first argument and an array of rules as the second argument.

const validation = new JustValidate('#form');

validation
  .addField('#name', [
    {
      rule: 'minLength',
      value: 3,
    },
    {
      rule: 'maxLength',
      value: 30,
    },
  ])
  .addField('#email', [
    {
      rule: 'required',
      errorMessage: 'Email is required',
    },
    {
      rule: 'email',
      errorMessage: 'Email is invalid!',
    },
  ]);

And that's it! Now our form is validated!

More

Please, check out the examples and documentation. Or try the playground.

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Modern, simple, lightweight (~5kb gzip) form validation library written in Typescript, with no dependencies (no JQuery!). Support a wide range of predefined rules, async, files, dates validation, custom error messages and styles, localization. Support writing custom rules and plugins.

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