Object.prototype.__lookupGetter__() - JavaScript 编辑

Deprecated

This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

The __lookupGetter__ method returns the function bound as a getter to the specified property.

Syntax

obj.__lookupGetter__(sprop)

Parameters

sprop

A string containing the name of the property whose getter should be returned.

Return value

The function bound as a getter to the specified property.

Description

If a getter has been defined for an object's property, it's not possible to reference the getter function through that property, because that property refers to the return value of that function. __lookupGetter__ can be used to obtain a reference to the getter function.

It is now possible to do this in a standardized way using Object.getOwnPropertyDescriptor() and Object.getPrototypeOf().

Examples

Standard-compliant and non-standard ways to get a property getter

var obj = {
  get foo() {
    return Math.random() > 0.5 ? 'foo' : 'bar';
  }
};

// Non-standard and deprecated way
obj.__lookupGetter__('foo');
// (function() { return Math.random() > 0.5 ? 'foo' : 'bar'; })

// Standard-compliant way
Object.getOwnPropertyDescriptor(obj, "foo").get;
// (function() { return Math.random() > 0.5 ? 'foo' : 'bar'; })

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Object.prototype.__lookupSetter__()
• get operator
• Object.getOwnPropertyDescriptor() and Object.getPrototypeOf()
• Object.prototype.__defineGetter__()
• Object.prototype.__defineSetter__()
• JS Guide: Defining Getters and Setters