legit.js

Lightweight objects and strings validation for Node.js.

Usage

Create a schema (i.e. define constraints) and use it to validate data.

There are two equivalent usages:

schema.test(data)
legit.mize(schema, data)

These functions return null if there was no error validating the data. If the data didn’t fit the schema, they return a description of the error (either a String, an Array, or a Map/Object).

    var schema = legit.Number().min(5).max(10);

    var err1 = schema.test(30);  // err1 = 'Greater than max'
    var err2 = schema.test(6);   // err2 = null

    // alternative usage:
    err1 = legit.mize(schema, 30);  // err1 = 'Greater than max'
    err2 = legit.mize(schema, 6);   // err2 = null

Note: The keyword “new” should not be used when creating an instance of a schema.

Real world example

Suppose you have some incoming network data and you want to validate it before using/processing it.

    // Create the schema
    var userSchema = legit.Map().strict()
        .key("user", legit.String().min(3).max(20))
        .key("age", legit.Number().min(21));
    
    // Validate incoming data
    var err = userSchema.test(data);

    if (err) {
        // Data did not fit the schema.
        // Check 'err' to learn what went wrong.
        console.log(err);
    }
    else {
        // Data successfully validated!
        // Now you can use/process it with confidence.
        ...
    }

Installing and Importing

Using NPM, run the following command in your project’s root directory.

$ npm install legitjs

In your Node.js program:

    var legit = require("legitjs");

legit.Any()

Accepts anything.

Example:

    var schema = legit.Any();
    schema.test("POTATO")   // null
    schema.test([1, 2, 3])  // null

legit.Null()

Accepts only null.

Example:

    var schema = legit.Null();
    schema.test("Hello")    // 'Not null'
    schema.test(null)       // null

legit.Boolean()

Accepts only Booleans.

Modifiers:

none(): Accepts null and undefined.

Example:

    var schema = legit.Bool();
    schema.test(123)    // 'Not a boolean'
    schema.test(null)   // 'Boolean is null or undefined'
    schema.test(true)   // null

    var schema2 = legit.Bool().none()
    schema2.test(null)   // null

legit.Number()

Accepts only Numbers.

Modifiers:

none(): Accepts null and undefined.
min(a): Sets minimum allowed value (a).
max(b): Sets maximum allowed value (b).

Example:

    var schema = legit.Number().min(-5).max(30);
    schema.test(-5);    // null
    schema.test(31);    // 'Greater than maximum'
    schema.test(true);  // 'Not a number'
    schema.test(null);  // 'Number is null or undefined'

legit.String()

Accepts only Strings.

Modifiers:

none(): Accepts null and undefined.
min(a): Sets minimum allowed length (a).
max(b): Sets maximum allowed length (b).
regex(e): Sets a regular expression to use (e).

Example:

    var schema = legit.String().max(12).regex(/(\w+)\s(\w+)/);
    
    schema.test("JohnSmith");
    // 'Regular expression didn't match'

    schema.test("John Smith");
    // null
    
    schema.test("John R. Smith");
    // 'Greater than maxmimum'

legit.Array()

Accepts only Arrays. Can be used recursively with all other schemas.

You have two options when using legit.Array():

Set a schema to validate all objects of the array by using .type(schema) once.
Set a different schema for each item by using .item(schema) once for each item, in the expected order.

Modifiers:

none(): Accepts null and undefined.
min(a): Sets minimum allowed length (a). Only affects same-type arrays.
max(b): Sets maximum allowed length (b). Only affects same-type arrays.
type(s): Sets a schema (s) to test all array items. Establishes array as same-type.
item(s): Sets a schema (s) to test a single item of the array. Establishes array as different-type.
strict(): Rejects arrays with length greater than expected. Only affects different-type arrays.

Example:

    // Same-type array
    var schema = legit.Array().max(4)
        .type(legit.Number().min(0).max(10));
        
    schema.test([1, 2, 3, 4]);
    // null
    
    schema.test([1, 2, 3, 4, 5]);
    // 'Greater than maxmimum'

    schema.test([5, 11]);
    // [null, 'Greater than maximum']
        
    // Different-type array
    var schema = legit.Array().strict()
        .item(legit.String().min(3).max(12))
        .item(legit.Number().min(21));
        
    schema.test(["John Smith", 25]);
    // null
    
    schema.test(["John", 25, true]);  
    // [ null, null,
    //   'More items than expected (Array in strict mode)' ]
    
    schema.test(["John Smith Jr.", 20]);
    // [ 'Greater than maximum', 'Less than minimum' ]

legit.Map()

Accepts only Maps/Objects. Can be used recursively with all other schemas.

Modifiers:

none(): Accepts null and undefined.
strict(): Rejects maps with unexpected keys.
key(n, s): Sets an expected key-value pair. n is the expected key and s is the schema that will be used to validate the value.

Example:

    var schema = legit.Map().strict()
        .key("user", legit.String().min(3).max(12))
        .key("age", legit.Number().min(21));

    schema.test({
        "user": "John Smith",
        "age": 25
    }) 
    // null
        
    schema.test({
        "user": "John Smith Junior",
        "age": 16
    })
    // { user: 'Greater than maximum',
    //    age: 'Less than minimum' }

Support/Contact

Feel free to contact me with questions, suggestions, or comments.

I hope you enjoy using legit.js as much as I enjoyed writing it.

If you come across any issues, please report them.