Xarg NPM | npm.io

xarg

A small tool for validating arguments in JavaScript

Install

npm install xarg --save

Usage

Every function will check if passed variable is defined and if it have a value of a specific type. This will throw an assertion error when values are not valid.

A list of available functions:

isArguments()
isArray()
isArrayBuffer()
isBoolean()
isBuffer()
isDate()
isDefined()
isEmpty()
isError()
isFinite()
isFunction()
isInteger()
isMap()
isNaN()
isNil()
isNull()
isNumber()
isObject()
isPlainObject()
isPromise()
isRegExp()
isSet()
isString()
isSymbol()
isTypedArray()
isWeakMap()
isWeakSet()

To test your arguments you need to pass an object with data. For example:

xarg.isArray({a: [], b:[1,2,3], c: {}})

Examples

Example #1

function hello(text, age) {
  xarg.isString({text});
  xarg.isNumber({age});
}
  
hello('John', 25); // OK
hello([]); // AssertionError [ERR_ASSERTION]: "text" should be of type String, but got: object
hello('John'); // AssertionError [ERR_ASSERTION]: "age" should be defined
hello('John', 'abc'); // AssertionError [ERR_ASSERTION]: "age" should be of type Number, but got: string

Example #2

class APIService {
  constructor(url) {
    xarg.isString({url});
  }

  post(json) {
    xarg.isObject({json});
  }
}

const service = new APIService('https://example.com');
service.post({ data: '123' }); // OK

new APIService([]); // AssertionError [ERR_ASSERTION]: "url" should be of type String, but got: object
new APIService({}); // AssertionError [ERR_ASSERTION]: "url" should be of type String, but got: object

const service = new APIService(123); // AssertionError [ERR_ASSERTION]: "age" should be of type Number, but got: string
service.post('123'); // AssertionError [ERR_ASSERTION]: "json" should be of type Object, but got: string