validate-value

validate-value

validate-value validates values against JSON schemas.

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Installation

$ npm install validate-value

Quick start

First you need to integrate validate-value into your application:

const { Value, isOfType } = require('validate-value');

If you use TypeScript, use the following code instead:

import { Value, isOfType } from 'validate-value';

Then, create a new instance and provide a JSON schema that you would like to use for validation:

const value = new Value({
  type: 'object',
  properties: {
    username: { type: 'string' },
    password: { type: 'string' }
  },
  additionalProperties: false,
  required: [ 'username', 'password' ]
});

Afterwards, you may use the validate function to validate a value:

const user = {
  username: 'Jane Doe',
  password: 'secret'
};

try {
  value.validate(user);
} catch (ex) {
  // ...
}

By default, the error message uses value as identifier and . as the separator for the object that is validated, but sometimes you may want to change this. Therefor, provide the desired identifier and separator as second parameter to the validate function:

const user = {
  username: 'Jane Doe',
  password: 'secret'
};

try {
  value.validate(user, { valueName: 'person', separator: '/' });
} catch (ex) {
  // ...
}

From time to time, you may not be interested in the actual error, but only in the fact whether the given object is valid or not. For these cases, use the isValid function:

const user = {
  username: 'Jane Doe',
  password: 'secret'
};

console.log(value.isValid(user));
// => true

Verifying that a variable is of a specific type

To verify that a variable is of a specific type, use the isOfType function. Hand over a value you would like to verify, and a JSON schema describing that type. The function returns true if the given variable matches the schema, and false if it doesn't:

const { isTypeOf } = require('validate-value');

const user = {
  username: 'Jane Doe',
  password: 'secret'
};

const schema = {
  type: 'object',
  properties: {
    username: { type: 'string' },
    password: { type: 'string' }
  },
  additionalProperties: false,
  required: [ 'username', 'password' ]
};

if (isOfType(user, schema)) {
  // ...
}

When using TypeScript, you may even specify a generic type parameter, and use the function as a type guard. Also it is recommended to use the constant values exported by validate-value instead of the string literals as above, as they are the type-safe versions of these literals:

import { isTypeOf, value as v }

interface User {
  username: string;
  password: string;
}

const user = {
  username: 'Jane Doe',
  password: 'secret'
};

const schema = {
  type: v.object,
  properties: {
    username: { type: v.string },
    password: { type: v.string }
  },
  additionalProperties: false,
  required: [ 'username', 'password' ]
};

if (isOfType<User>(user, schema)) {
  // ...
}

Running quality assurance

To run quality assurance for this module use roboter:

$ npx roboter