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When creating objects or prototypes using Object.defineProperties or Object.defineProperty it make your code look really verbose by all the property descriptions that it needs. Most of the time, they are the same. They either make your properties writable, readable or prevents them from being enumerable. So basically:

Predefine makes Object.defineProperties your human readable and manageable.


npm install --save predefine

Getting started

Let's start with a basic example of predefine usage:

var predefine = require('predefine');
function Base() {
  var readable = predefine(this, { configurable: false, enumerable: false })
    , writable = predefine(this, predefine.WRITABLE);
  readable('prop', 'value');
  writable('data', []);
Base.writable = predefine(Base.prototype, predefine.WRITABLE);
Base.writable('foo', 'bar');

As you can see from the snippet above, it's really easy to see which properties are made readable and which one's are writable.


This allows you to add Backbone inspired .extend functionality to your constructors. This makes inheriting a lot easier and readable. See the extendible module in npm for information.

function Foo() {}
Foo.extend = predefine.extend;
var Bar = Foo.extend({
  method: function () {}


Test if a given object is a valid Object description to it can be used with Object.defineProperty, Object.defineProperties and Object.create.

predefine.descriptor({ foo: 'bar' });                       // false 
predefine.descriptor({ value: 'bar' });                     // true 
predefine.descriptor({ value: 'bar', enumerable: false });  // true 
predefine.descriptor({ value: 'bar', foo: 'bar' });         // false 


This is a simple helper function to create descriptions that can be used within Object.create and Object.defineProperties.

var data = Object.create(null, predefine.create('foo', { 
  value: 'bar' 
var data = Object.create(null, predefine.create('foo', {
  value: 'bar'
}, predefine.READABLE));
var data = Object.create(null, predefine.create('foo', 'bar', predefine.READABLE));


Removes all enumerable properties from a given object, with the ability to keep white listed properties.

var data = { foo: 'bar', bar: 'foo' };
predefine.remove(data);           // The data variable is now an empty object. 
predefine.remove(data, ['foo']);  // The foo property is kept. 
var readable(data);
readable('baz', 'baz');
predefine.remove(data);           // Only `baz` is left. 


Merge two objects in to one single object. This supports deep merging.

var result = predefine.merge({ foo: 'bar' }, { bar: 'foo' });


Mixin two Objects, which also transfers properties that are set using Object.defineProperty.

var result = predefine.mixin({ foo: 'bar' }, { bar: 'foo' });