function.create

Function.create allows you to create named functions easily in JavaScript.

Function.create

This allows you to create named functions easily in JavaScript. Tested browsers:

  • IE 8
  • Chrome
  • Firefox
  • Safari

It is similar to the sketched Function.create in ECMAScript (two years old). The proposal was never accepted, so this function is not based on any standards, but it's still very useful.

Download:

Installing:

npm install function.create

Loading it in Node.JS:

require('function.create'); // now loaded globally 

Loading it in the browser:

<script src="Function.create.js"></script>

Two functions are provided:

  • Function.create(name, call[, construct[, proto]])
  • Function.getDisplayNameOf(f)

The proto argument sets the prototype of the newly created function. This is available in all browsers except MSIE, where it is simulated by copying the whole prototype chain.

Example 1 (creating unnamed function):

var anon = Function.create(null, function(str) {
  console.log('anon called:', str);
});
 
anon('Hello, anon!');

Example 2 (creating simple named function):

var simple = Function.create('simple', function(str) {
  console.log('simple called:', str);
});
 
console.log(simple.name); // "simple" 
simple('Hello, simple!');

Example 3 (creating simple named constructor):

var Constr = Function.create('Constr', function(n) {
  this.= n;
});
Constr.prototype.say = function(text) {
  console.log('say: ' + text + '' + this.+ '!');
};
 
console.log(Constr.name); // "Constr" 
var c = new Constr('simple named constructor');
c.say('Bonjour'); // say: Bonjour, simple named constructor! 

Example 4 (creating named function and constructor):

var Person = Function.create('Person', function(name) {
  return new Person(name);
}, function(name) {
  this.name = name;
});
 
console.log(Person.name); // "Person" 
var p1 = new Person('Bobby');
var p2 = Person('Bobby');
console.log('Same person?', p1.name === p2.name); // true 

Example 5 (getting name of function):

var func = function fancyFunction() {};
console.log('Function name:', Function.getDisplayNameOf(func));

Example 6 (named classes):

function createClass(nameproperties) {
  var Class = Function.create(name, function() {
    if (typeof(this.initialize) === 'function') {
      this.initialize.apply(this, arguments);
    }
  });
  Class.prototype = properties;
  Class.prototype.constructor = Class;
  return Class;
}
 
var Person = createClass('Person', {
  initializefunction(name) {
    this.name = name;
  },
  getNamefunction() {
    return this.name;
  }
});
var andy = new Person('Andy');
console.log(andy instanceof Person); // true 
console.log(andy.getName()); // "Andy" 

Example 7 (functor, or the story about function inheriting object):

function createFunctor(nameproperties) {
  return Function.create(name, function() {
    if (typeof(this.invoke) === 'function') {
      this.invoke.apply(this, arguments);
    }
  }, null, properties);
}
 
function Module() {}
Module.prototype = new Function();
Module.prototype.constructor = Module;
 
Module.prototype.say = function(message) {
  console.log('I want to say: ' + message);
};
Module.prototype.invoke = function(ab) {
  this.say(+ ' + ' + b + ' = ' + (+ b));
  return a + b;
};
 
var M = createFunctor('Module', new Module());
console.log(M.name); // "Module" 
console.log(typeof(M)); // "function" 
console.log(instanceof Module); // true, in all browsers except MSIE 
M(20, 22); // outputs "I want to say: 20 + 22 = 42"