Web_Dev_Grad

Validation in JavaScript is the process of checking whether data entered into a form or provided in code meets the expected rules or formats. It helps prevent bugs, improves code quality, and ensures a smooth user experience.

JSLint is one of the earliest JavaScript linters. A linter is a tool that checks your code for common mistakes, bad practices, and syntax issues before the code even runs.

What does a linter do?

• Identifies typos, unused variables, and undeclared variables
• Enforces consistent code style (like spacing and semicolons)
• Encourages best practices to prevent potential bugs
• Can be integrated into your code editor or build proces

Popular modern alternatives include ESLint and JSHint, but JSLint laid the groundwork for them.

While you can write your own validation logic in plain JavaScript, using a library saves time and reduces the chance of errors.

just-validate is a lightweight and flexible library for client-side form validation. It's easy to set up and supports features like:

• Real-time validation
• Custom error messages
• Async validation (e.g., checking username availability)

You can install it using npm: npm install just-validate.

// An example of just-validate being used
// Import it at the top of your file
import JustValidate from 'just-validate';

// Define a validator
const validator = new JustValidate('#my-form');

// Add customisation to the validator
validator
  .addField('#email', [
    {
      rule: 'required',
    },
    {
      rule: 'email',
    },
  ]);