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126 lines
4.2 KiB
Markdown
126 lines
4.2 KiB
Markdown
<a href="http://hapijs.com"><img src="https://raw.githubusercontent.com/hapijs/assets/master/images/family.png" width="180px" align="right" /></a>
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# joi
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Object schema description language and validator for JavaScript objects.
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[](https://travis-ci.org/hapijs/joi)
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## Introduction
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Imagine you run facebook and you want visitors to sign up on the website with real names and not something like `l337_p@nda` in the first name field. How would you define the limitations of what can be inputted and validate it against the set rules?
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This is joi, joi allows you to create *blueprints* or *schemas* for JavaScript objects (an object that stores information) to ensure *validation* of key information.
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# Installation
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```cli
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npm install --save @hapi/joi
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```
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## API
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See the detailed [API Reference](https://github.com/hapijs/joi/blob/v15.1.0/API.md).
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## Example
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```javascript
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const Joi = require('@hapi/joi');
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const schema = Joi.object().keys({
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username: Joi.string().alphanum().min(3).max(30).required(),
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password: Joi.string().regex(/^[a-zA-Z0-9]{3,30}$/),
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access_token: [Joi.string(), Joi.number()],
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birthyear: Joi.number().integer().min(1900).max(2013),
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email: Joi.string().email({ minDomainSegments: 2 })
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}).with('username', 'birthyear').without('password', 'access_token');
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// Return result.
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const result = Joi.validate({ username: 'abc', birthyear: 1994 }, schema);
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// result.error === null -> valid
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// You can also pass a callback which will be called synchronously with the validation result.
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Joi.validate({ username: 'abc', birthyear: 1994 }, schema, function (err, value) { }); // err === null -> valid
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```
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The above schema defines the following constraints:
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* `username`
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* a required string
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* must contain only alphanumeric characters
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* at least 3 characters long but no more than 30
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* must be accompanied by `birthyear`
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* `password`
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* an optional string
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* must satisfy the custom regex
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* cannot appear together with `access_token`
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* `access_token`
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* an optional, unconstrained string or number
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* `birthyear`
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* an integer between 1900 and 2013
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* `email`
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* a valid email address string
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* must have two domain parts e.g. `example.com`
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## Usage
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Usage is a two steps process. First, a schema is constructed using the provided types and constraints:
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```javascript
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const schema = {
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a: Joi.string()
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};
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```
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Note that **joi** schema objects are immutable which means every additional rule added (e.g. `.min(5)`) will return a
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new schema object.
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Second, the value is validated against the defined schema:
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```javascript
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const {error, value} = Joi.validate({ a: 'a string' }, schema);
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// or
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Joi.validate({ a: 'a string' }, schema, function (error, value) { });
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```
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If the input is valid, then the `error` will be `null`, otherwise it will be an `Error` object providing more information.
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The schema can be a plain JavaScript object where every key is assigned a **joi** type, or it can be a **joi** type directly:
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```javascript
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const schema = Joi.string().min(10);
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```
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If the schema is a **joi** type, the `schema.validate(value, callback)` can be called directly on the type. When passing a non-type schema object,
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the module converts it internally to an object() type equivalent to:
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```javascript
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const schema = Joi.object().keys({
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a: Joi.string()
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});
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```
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When validating a schema:
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* Values (or keys in case of objects) are optional by default.
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```javascript
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Joi.validate(undefined, Joi.string()); // validates fine
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```
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To disallow this behavior, you can either set the schema as `required()`, or set `presence` to `"required"` when passing `options`:
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```javascript
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Joi.validate(undefined, Joi.string().required());
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// or
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Joi.validate(undefined, Joi.string(), /* options */ { presence: "required" });
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```
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* Strings are utf-8 encoded by default.
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* Rules are defined in an additive fashion and evaluated in order, first the inclusive rules, then the exclusive rules.
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## Browsers
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Joi doesn't directly support browsers, but you could use [joi-browser](https://github.com/jeffbski/joi-browser) for an ES5 build of Joi that works in browsers, or as a source of inspiration for your own builds.
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