Legit.js

A simple input validation JavaScript library

Requirements:

• Ensure.js (https://github.com/eduard44/ensure)

On the browser:

On the browser, legit is available as a global object:

1- Install using Bower:

bower install legit

2- Make sure ensure.js is also included in your project (Bower automatically downloads it as a dependency):

<script src="bower_components/ensure.js/ensure.js"></script>

3- Include the JS file on your project:

<script src="bower_components/legit/dist/legit.js"></script>

4- Use it!

On node.js:

On node.js, legit is available as a module:

1- Install using npm:

npm install legit.js

2.- Include the library in your project:

var legit = require('legit.js');

3.- Use it!

Usage example:

Legit works by definining a rule set using a Validator class and then executing the validator on some input object:

// Aliases for convenience
var Validator = legit.Validator,
    MinMaxLengthRule = legit.MinMaxLengthRule,
    InArrayRule = legit.InArrayRule,
    RequiredRule = legit.RequiredRule,
    ValidationError = legit.ValidationError;
 
// Create a new validator instance
var userValidator = new Validator();
 
userValidator.addRule('first_name', new MinMaxLengthRule(1, 20));
userValidator.addRule('last_name', new MinMaxLengthRule(1, 20));
userValidator.addRule('type', new InArrayRule(['admin', 'customer']), 'User must have a valid type');
 
// This should not fail:
try {
    userValidator.validate({
        'first_name': 'John',
        'last_name': 'Appleseed',
        'type': 'admin'
    });
} catch (error) {
    if (error instanceof ValidationError) {
        console.log(error.getMessages());
    } else {
        console.log('We got some other kind of error :(');
    }
}
 
// This should fail:
try {
    userValidator.validate({
        'first_name': 'JohnJohnJohnJohnJohnJohn',
        'last_name': '',
        'type': 'lulz'
    });
} catch (error) {
    if (error instanceof ValidationError) {
        console.log(error.getMessages());
    } else {
        console.log('We got some other kind of error :(');
    }
}

It is also possible to define rules in the constructor of the validator for a shorter definition block. A field can contain one rule or an array of rules:

var userValidator = new Validator({
    first_name: [new MinMaxLengthRule(1, 20), new RequiredRule()],
    last_name: new MinMaxLengthRule(1, 20),
    type: new InArrayRule(['admin', 'customer'])
});

Included rules:

Legit.js comes with some built-in rules:

• MinMaxLengthRule(min, max): Expects that the length of the field value is within a certain range
• MinMaxRule(min, max): Expects that the field value is within a certain range
• InArrayRule(allowedElements): Expects that the field value is contained in the allowedElements array
• RequiredRule(): Requires a field to be defined in the input object
• EqualsFieldRule(fieldName): Expects that one field equals another field
• TypeRule(ensureType): Expects that the field is of a certain ensure.js type
• RegexMatchRule(regex): Expects that the field matches a certain JS regular expression

Extending:

It is possible to extend the default rule set by creating rule objects that have ValidationRule as their prototype. The main function to implement is execute(value, fields, property), which returns true if the input is valid or false if its not.

The example below is a rule that checks if the input is equal to hello or hello world (if true is provided in the constructor):

var HelloRule = function (checkWorld) {
    // Call parent constructor
    legit.ValidationRule.call(this, arguments)
 
    // Save parameters
    this.checkWorld = checkWorld;
}
 
HelloRule.prototype = new legit.ValidationRule();
 
// The execute method performs the validation check.
// It is expected that it returns true if the field is valid. False, otherwise.
HelloRule.prototype.execute = function (inputValue, fields, property) {
    if (this.checkWorld) {
        return inputValue === 'hello world';
    }
 
    return inputValue === 'hello';
};
 
// (Optional) Get a custom error message for this rule
HelloRule.prototype.getMessage = function (fieldName) {
    if (this.checkWorld) {
        return fieldName + ' should be equal to "hello world"';
    }
 
    return fieldName + ' should be equal to "hello"';
};