const nJ = require('normalize-json'); // a schema looks like this! let validator = nJ({ name: [String, 30], // a string with <= 30 characters age: [Number, 0, 100], // a number between 0 and 100, inclusive color: ['red', 'yellow', 'blue'] // must be one of these three values }); // here's how we might validate/normalize an object let obj = { name: ' Nigel ', // this string will be trimmed! age: 23, color: 'blue', someUndefinedField: undefined // undefined fields will be stripped out }; let result = validator(obj); // 'result' is a new object; 'obj' has not been changed console.log(result); // { name: 'Nigel', age: 23, color: 'blue' } // here's a bad object; this will fail validation let badObj = { name: 'Somebody', age: 'not a number', color: null, extraField: 'should not be here' }; try { let result = validator(badObj); } catch (err) { console.log(err.message); // will give the first found error: "age is not a number" }