TypedFunc

Allows creating Typed Functions in Javascript with Typed Arguments and default argument values. All Optional.

Convensions

This library is split in two, basically divided by convension, so whether you hate callbacks (Classical convension), or love to Node (Node callback convension). This library caters for your taste. Its core features are applied splightly differently for each convention (as appropriate). But Both conventions will allow you to declare Types for your arguments, as well as default values if arguments are undefined .

• Classical Convension - Will throw errors when invalid argument types are passed, or if a function returns an invalid type.

  Typed Arguments

  Typed Functions

  Argument Defaults

• Node Callback Convension - Will pass the relivant error as the first parameter of your callback, if an argument type is invalid, or if values passed to your callback are of an invalid type.

  Typed Arguments

  Typed Functions

  Argument Defaults

Setup

You need to specify your preference of convension before using new TypedFunc() by doing the following:

TypedFunc({
	errors: "Throw", // either "Throw" or "Node"
	trace: false // optional includes line limbers for debugging.
})

The Classical Convention

#1a Typed Arguments

You can define any types you like for your arguments: {x: {type: "xxxx"}}, a string (ie: "number", "object", "string") denotes a typeof x === xxxx check, and an Object - such as a new Person() can be defined as {x: {type: Person}} and will perform an x instanceof Person check.

// Create TypedFunc
var classical = new TypedFunc({x: {type: "string"}}, function(x){
	return x
})

// Call TypedFuncs

classical()
// throws error invalid argument type

classical(23)
// throws error invalid argument type

classical("Hello World")
// returns "Hello World"

If you'd like to be less strict, you could also specify Multiple types for an argument, by putting them in an array, like so:

var classical = new TypedFunc({x: {type: ["string", "number"]}}, function(x){
	return x
})

// now it will accept either a "string" or an "number". neat!

#1b Typed Functions

You can define a function as a sprecific Type. This performs a check that your function returns the required type otherwise it will throw an error.

// Create TypedFunc
var classical = new TypedFunc("string", {}, function(x){
	return x
})

// Call TypedFuncs

classical()
// throws error invalid function return type

classical(23)
// throws error invalid function return type

classical("Hello World")
// returns "Hello World"

Again, you can specify Multiple Types for the return value, by providing an array, like so:

var classical = new TypedFunc(["string", "number"], {}, function(x){
	return x
})

// now it will return either a "string" or an "number". and if not, will throw an error.

#1c Argument Defaults

Argument defaults act the same in both convensions, and mearly check for undefined arguments and if found replace with provided defaults.

// Create TypedFunc
var classical = new TypedFunc({a {default: "A"}}, function(a){
	return a
})

// Call TypedFunc
classical()
// returns "A"

The Node Callback Convension

The Style, follows the function(err, data) {} convension from NodeJS. where errors are passed to the function itself instead of being Thrown.

#2a Typed Arguments

You can define any types you like for your arguments: {x: {type: "xxxx"}}, a string (ie: "number", "object", "string") denotes a typeof x === xxxx check, and an Object - such as a new Person() can be defined as {x: {type: Person}} and will perform an x instanceof Person check.

// Create TypedFunc
var nodeJSConv = new TypedFunc({a: {type: "string"}}, function(a, callback){
	callback(null, "success : " + a)
})

// Call TypedFuncs

nodeJSConv(23 ,function(err, data){
	if (err) console.log("Error: ", err)
	else console.log("Success: ", data)
});
// outputs Error: invalid argument type

nodeJSConv("Hello World", function(err, data){
	if (err) console.log("Error: ", err)
	else console.log("Success: ", data)
});
// outputs Success: Hello World

You can also specify Multiple argument types by providing them as an array, like so:

// Create TypedFunc
var nodeJSConv = new TypedFunc({a: {type: ["string", Person]}}, function(a, callback){
	callback(null, a)
})

// Call TypedFuncs

var x = new Person("Dave");

nodeJSConv(x ,function(err, data){
	if (err) console.log("Error: ", err)
	else console.log("Success: ", data)
});

// this will output Success: [Object Person] ie: would work for both `numbers` and `Persons` and pass a non null error for all other argument types.

#2b Typed Functions

Applying the Typed Function return concept to Callback style functions is rather tricky, but TypedFunc achieves this by replacing your callback with an interceptor and evaluating the arguments passed to it. So as can be seen below if the value passed to callback is not of the type number then a non null error will be passed to the callback.

// Create TypedFunc
var nodeJSConv("number", function(a, callback) {
	callback(null, "Success: " + a)
})

// Call TypedFunc
nodeJSConv("Test", function(err, data) {
	if (err) console.log("Error: ", err)
	else console.log("Success: ", data)
})  
// outputs Error: Invalid function return type

#2c Argument Defaults

Argument defaults act the same in both convensions, and mearly check for undefined arguments and if found replace with provided defaults.

// Create TypedFunc
var nodeJSConv({a: {default: "B"}}, function(a, callback) {
	callback(null, "Success: " + a)
})

// Call TypedFunc
nodeJSConv("Test", function(err, data) {
	if (err) console.log("Error: ", err)
	else console.log("Success: ", data)
})  
// ouputs Success: B

MIT Licenced

by Christopher de Beer 2012

@christopherdb