Created
April 19, 2014 15:20
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Backbone's extend method
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// Helper function to correctly set up the prototype chain, for subclasses. | |
// Similar to `goog.inherits`, but uses a hash of prototype properties and | |
// class properties to be extended. | |
var extend = function(protoProps, staticProps) { | |
var parent = this; | |
var child; | |
// The constructor function for the new subclass is either defined by you | |
// (the "constructor" property in your `extend` definition), or defaulted | |
// by us to simply call the parent's constructor. | |
if (protoProps && _.has(protoProps, 'constructor')) { | |
child = protoProps.constructor; | |
} else { | |
child = function(){ return parent.apply(this, arguments); }; | |
} | |
// Add static properties to the constructor function, if supplied. | |
_.extend(child, parent, staticProps); | |
// Set the prototype chain to inherit from `parent`, without calling | |
// `parent`'s constructor function. | |
var Surrogate = function(){ this.constructor = child; }; | |
Surrogate.prototype = parent.prototype; | |
child.prototype = new Surrogate; | |
// Add prototype properties (instance properties) to the subclass, | |
// if supplied. | |
if (protoProps) _.extend(child.prototype, protoProps); | |
// Set a convenience property in case the parent's prototype is needed | |
// later. | |
child.__super__ = parent.prototype; | |
return child; | |
}; |
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