gistfile1.js

//JS functions, prototypes
var ok_for_kids = function(movie) {
  // or: function ok_for_kids(movie) { ... }
  return( /^G|PG/.test(movie.rating) );
}
ok_for_kids; // => a function
ok_for_kids({title: 'The Godfather', rating: 'R'});  // => a function call
 
myfunc = ok_for_kids;
myfunc({title: 'The Godfather', rating: 'R'});  // => a function call
 
 
var Movie = function(title,year,rating) {
  // or:  function Movie(title,year,rating) {...}
  this.title = title;
  this.year = year;
  this.rating = rating;
  this.ok_for_kids = function() { // "instance method"
    // return() must be explicit
    return( /^G|PG/.test(this.rating) );
  };
  this.full_title = function() { // "instance method"
    return(this.title + ' (' + this.year + ')');
  };
};
 
// using 'new' makes Movie the new objects prototype:
var pianist = new Movie('The Pianist', 2002, 'R');
var chocolat = new Movie('Chocolat', 2000, 'PG-13');
pianist.full_title(); // => "The Pianist (2002)"
chocolat.full_title(); // => "Chocolat (2000)"
chocolat.ok_for_kids(); // => true
// adding methods to an individual object:
pianist.title_with_rating = function() {
    return (this.title + ': ' + this.rating);
}
pianist.title_with_rating(); // => "The Pianist: R"
chocolat.title_with_rating(); // => Error: 'undefined' not a function
// but we can add functions to prototype "after the fact":
Movie.prototype.title_with_rating = function() {
    return (this.title + ': ' + this.rating);
}
chocolat.title_with_rating(); // => "Chocolat: PG-13"
// we can also invoke using 'apply' -- 'this' will be bound to the
//  first argument:
Movie.full_title.apply(chocolat); // "Chocolat (2000)"
// BAD: without 'new', 'this' is bound to global object!!
juno = Movie('Juno', 2007, 'PG-13'); // DON'T DO THIS!!
juno;               // undefined
juno.title;         // error: 'undefined' has no properties
juno.full_title();  // error: 'undefined' has no properties