dbc is a small library for design-by-contract defensive coding in javascript.
It focuses especially on type assertions in an attempt to provide a small compensation for JavaScript's unfortunate dynamicness. Some of the ideas were borrowed from ristretto-js.
The core features are:
- validate values against a specification
- generate type constructors from a specification
- runtime validation of function arguments and return value (via the
wrapcombinator)
Install
npm install dbc
Features
Check a value:
dbc.type(1, 'number', 'optional error message');
dbc.isFunction(function () {}, 'optional error message');
dbc.functionArity(function () {}, 0, 'optional error message');
// etcCheck an object:
dbc.check({
a: 1,
b: "cat in the hat",
c: function (f, s) { return f + s; }
}, {
a: [
{validator: 'required', args: ['optional error message']},
{validator: 'type', args: ['number']},
{validator: 'custom', args: [ function (v) {
// custom validator function should return a boolean
return v > 0;
}]}
],
b: [{validator: 'type', args: ['string']}],
c: [{validator: 'isFunction'}, {validator: 'functionArity', args: [2, {message: 'This is a more advanced error object', field: 'c'}]}]
});Validate an object (same as check except that it returns an array of errors instead of throwing an exception at the first error):
dbc.validate({
a: 1,
b: "cat in the hat",
c: function (f, s) { return f + s; }
}, {
a: [
{validator: 'required', args: ['optional error message']},
{validator: 'type', args: ['number']},
{validator: 'custom', args: [ function (v) {
// custom validator function should return a boolean
return v > 0;
}]}
],
b: [{validator: 'type', args: ['string']}],
c: [{validator: 'isFunction'}, {validator: 'functionArity', args: [2, {message: 'This is a more advanced error object', field: 'c'}]}]
}); // create a constructor that automatically validates its schema
var AjaxOptions = dbc.makeConstructor({
type: [
{validator:'type', args:['string']},
{validator:'oneOf', args:[['GET','POST','PUT','DELETE']]}
],
url: [{validator:'type',args:['string']}],
dataType: [{validator:'type',args:['string?']}]
});
// define a function that validates its argument (is a string) and its return type (is an AjaxOptions)
AjaxOptions.fromCorsRequest = dbc.wrap(function (corsRequestText) {
return new AjaxOptions(new CorsRequest(corsRequestText).getJSON());
}, {
0: [{validator:'type', args:['string']}]
}, [{validator:'isInstance',args:[AjaxOptions]}]);Test
npm install -g jasmine-node
jasmine-node --coffee spec/
