const transformer = require('transformer'); const book = { // object to process name: 'The Adventures of Tom Sawyer', author: { name: 'Mark Twain' }, reviews: [ { author: 'Leo Tolstoy', text: 'Great novel', visible: true }, { author: 'Fyodor Dostoyevsky', text: 'Very interesting' } ] }; const schema = { name: { $filter: 'trim', $validate: { required: true, string: true } }, author: { $validate: { required: true }, name: { $filter: function(value) { // you can use function for filtration // this example has the same behaviour as built-in "trim": it trims only strings return typeof value === 'string' ? value.trim() : value; }, $validate: { required: true, string: true } } }, reviews: [{ // define schema for array items author: { $filter: ['trim', /* another filter */], // you can use array of filters $validate: { required: true, string: true } }, text: { $filter: [['trim', { /* some options */ }]], // you can pass additional options to filter if needed $validate: { required: true, string: true } }, visible: { $default: true, // default value will be set when actual value of property is undefined $filter: 'toBoolean' // always returns boolean } }] }; const transform = function(object, schema) { return transformer(object, schema) // you can run plugins in the order you want, but this one looks good .default() .filter() .validate() .clean() .result; }; transform(book, schema) .then(result => { // result is transformed object console.log('Result', result); }) .catch(err => { if (err instanceof transformer.plugins.validate.ValidationError) { // you have validation errors console.log('Validation errors', err.errors); } else { // application error (something went wrong) console.log('Application error', err); } });