Object.prototype.__defineGetter__() - JavaScript 编辑

This feature is deprecated in favor of defining getters using the object initializer syntax or the Object.defineProperty() API. While this feature is widely implemented, it is only described in the ECMAScript specification because of legacy usage. This method should not be used since better alternatives exist.

The __defineGetter__ method binds an object's property to a function to be called when that property is looked up.

Syntax

obj.__defineGetter__(prop, func)

Parameters

prop

A string containing the name of the property to bind to the given function.

func

A function to be bound to a lookup of the specified property.

Return value

undefined.

Description

The __defineGetter__ allows a getter to be defined on a pre-existing object.

Examples

Non-standard and deprecated way

var o = {};
o.__defineGetter__('gimmeFive', function() { return 5; });
console.log(o.gimmeFive); // 5

Standard-compliant ways

// Using the get operator
var o = { get gimmeFive() { return 5; } };
console.log(o.gimmeFive); // 5

// Using Object.defineProperty
var o = {};
Object.defineProperty(o, 'gimmeFive', {
  get: function() {
    return 5;
  }
});
console.log(o.gimmeFive); // 5

Specifications

Browser compatibility

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See also

• Object.prototype.__defineSetter__()
• get operator
• Object.defineProperty()
• Object.prototype.__lookupGetter__()
• Object.prototype.__lookupSetter__()
• JS Guide: Defining Getters and Setters
• [Blog Post] Deprecation of __defineGetter__ and __defineSetter__
• bug 647423