Object.prototype.__defineSetter__()
Warning: This feature is deprecated in favor of defining setters using the
object initializer syntax
or the Object.defineProperty()
API.
However, as it is widely implemented and used on the Web, it is very unlikely that browsers will stop implementing it.
The __defineSetter__
method binds an object's property to
a function to be called when an attempt is made to set that property.
Syntax
__defineSetter__(prop, fun)
Parameters
prop
-
A string containing the name of the property to be bound to the given function.
fun
-
A function to be called when there is an attempt to set the specified property. This function takes the form
function(val) { . . . } ``` - `val` - : An alias for the variable that holds the value attempted to be assigned to `prop`.
Return value
Description
The __defineSetter__
method allows a setter to be defined on a pre-existing object.
Examples
Non-standard and deprecated way
var o = {};
o.__defineSetter__('value', function(val) { this.anotherValue = val; });
o.value = 5;
console.log(o.value); // undefined
console.log(o.anotherValue); // 5
Standard-compliant ways
// Using the set operator
var o = { set value(val) { this.anotherValue = val; } };
o.value = 5;
console.log(o.value); // undefined
console.log(o.anotherValue); // 5
// Using Object.defineProperty
var o = {};
Object.defineProperty(o, 'value', {
set: function(val) {
this.anotherValue = val;
}
});
o.value = 5;
console.log(o.value); // undefined
console.log(o.anotherValue); // 5
Specifications
Specification |
---|
ECMAScript Language Specification # sec-object.prototype.__defineSetter__ |
Browser compatibility
BCD tables only load in the browser
See also
- Polyfill of
Object.prototype.__defineSetter__
incore-js
Object.prototype.__defineGetter__()
set
operatorObject.defineProperty()
Object.prototype.__lookupGetter__()
Object.prototype.__lookupSetter__()
- JS Guide: Defining Getters and Setters
- [Blog Post] Deprecation of __defineGetter__ and __defineSetter__
- bug 647423