Javascript Traits Pattern Resources

Question

Could anyone recommend good resources for using traits in javascript? After some searching I mainly find articles about libraries that provide traits functionality, but I was curious about best practices on how to implement traits without a library.

I came across this post on SO, are there any other approaches? Traits in javascript

Any real world examples would be welcome as well.

Thanks.

Answer 1

I would suggest something simple, along the lines of:

1. Let traits be defined as standard JavaScript objects.

   var equalsTrait = {
       eq: function(obj) {
           return this == obj
       },
       neq: function(obj) {
           return ! this.eq(obj)
       }
   };
   

2. Write a function to extend a given class with your traits (and bind it to a sensible location in the global scope):

   window.Traits = {};
   Traits.addToClass = function(traits, cls) {
       for (var key in traits) {
           if (cls.prototype[key]) {
               alert("Class " + cls + " already has a method named " + key + "!");
           }
           else {
               cls.prototype[key] = traits[key];
           }
       }
   }
   

3. Profit!

Answer 2

Some (limited) information about traits in the trait.js library

Not about Javascript, but a good paper about inheritance systems and traits "Traits: A Mechanism for Fine-grained Reuse". A description of implementation details can be found in "Applying Traits to the Smalltalk Collection Hierarchy". More papers of this type listed on this page.