surely

Can I add runtime type checking to JavaScript?

Surely you can't be serious.

I am serious... and don't call me Shirley.

Install

npm install surely

Example

var fs = require('fs');
var Surely = require('surely');


// --- Asynchronous error generation ---
var read = Surely
            .string('filename')   // First argument is a string
            .object('options')    // Second argument is an object
            .callback('callback') // Second/Third argument is a callback function
            .wrap(fs.readFile);

read(null, {}, function(err, data) {
  console.log(err);
  // [Error: Missing parameter: filename]
});


// --- Synchronous error generation ---
var readSync = Surely
                .string('filename')     // First argument is a string
                .object('options?')     // Second argument is an optional object
                .wrap(fs.readFileSync);
var data = readSync(['foo.txt', 'bar.tar.gz']);
console.log(data);
// [TypeError: Expected string for "filename"]


// --- Calling wrapped functions with objects ---
var values = Surely.number('num').string('str').regex('reg').wrap(function(num, str, reg) {
  return [num, str, reg];
});

var myvals = values({
  num: 123,
  str: 'foo',
  reg: /^this\sis\sregex$/
});

console.log(myvals);
// [123, 'foo', /^this\sis\sregex$]

// --- Using defaults ---
var random = Surely.number('min', 0).number('max', 100).wrap(function(min, max) {
  return min + Math.floor(Math.random() * (max - min + 1));
});

console.log(random());
// A random value between 0 and 100

console.log(random(10));
// A random value between 10 and 100

console.log(random(10, 20));
// A random value between 10 and 20

Types

Surely comes with a set of default types. You can define your own types or override the default types with your own methods.

Default Types

• array
• bool
• callback
• date
• func
• number
• object
• regex
• string

Surely.add(name, testFunction)

You can add types by using the add method with a String name and Function test function.

var Surely = require('surely');

Surely.add('int', function(val) {
  return typeof val === 'number' && Math.floor(val) === val;
});

var double = Surely.int('num').wrap(function(num) {
  return num * 2;
});

console.log(double(3.1));
// [TypeError: Expected int for 'num']

Surely.add(object)

You can also add types by using the add method with an object that contains key names and function values. Internally, surely uses this method to add the Default Types.

var Surely = require('surely');

var typetest = function(type) {
  return function(val) {
    return typeof val === type;
  };
};

Surely.add({
  'number': typetest('number'),
  'string': typetest('string'),
  'array': Array.isArray
});

Usage

Surely uses a builder pattern to construct a wrapped function.

Type(name, [defaultValue])

Each type (from the list of Default Types above) is a method that is called with one required name argument and one optional defaultValue argument. To make an argument optional, append a ? to the end of the name.

var Surely = require('surely');

var log = Surely
  .string('message')                // 'message' string param
  .object('data?')                  // 'data' object param that is optional
  .func('logger', console.log)      // a logging function that defaults to console.log
  .wrap(
function(message, opt_data, logger) {
  if (opt_data) {
    logger(message, opt_data);
  } else {
    logger(message);
  }
});

// Call log with parameters
log('hello there');
// hello there

// Call log with an object
log({
  message: 'Data overload',
  data: {overload: true}
});
//  Date overload { overload: true }

Retains context

Using Surely in a more Object Oriented way works, too. Scope is preserved in wrapped functions.

function Silo() {
  this.population = 5000;
}

Silo.prototype.setNumber = Surely.number('siloNumber').wrap(function(siloNumber) {
  this.number = siloNumber;
});

var silo = new Silo();

console.log(silo.number);
// undefined

silo.setNumber(18);

console.log(silo.number);
// 18

The MIT License

Copyright (c) 2014 Michael Maelzer

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.