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Binds an object property to a function to be called when there is an attempt to set that property.


{set prop(val) { . . . }}


the name of the property to bind to the given function
an alias for the variable that holds the value attempted to be assigned to prop


In JavaScript, a setter can be used to execute a function whenever a specified property is attempted to be changed. Setters are most often used in conjunction with getters to create a type of pseudo-property. It is not possible to simultaneously have a setter on a property that holds an actual value.

JavaScript 1.8.1 note

Starting in JavaScript 1.8.1, setters are no longer called when setting properties in object and array initializers.

JavaScript 1.8.5 note

Starting in JavaScript 1.8.5, set operator:

A setter can be removed using the delete operator.


Defining a setter with the set operator

This will define a pseudo-property current of object o that, when assigned a value, will update log with that value:

var o = {
  set current (str) {
    return this.log[this.log.length] = str;
  log: []

Note that current is not defined and any attempts to access it will result in undefined.

Removing a setter with the delete operator

delete o.current;


Specification Status Comment
ECMAScript 5.1 (ECMA-262)
The definition of 'set' in that specification.
ECMAScript 6 (ECMA-262)
The definition of 'set' in that specification.

Browser compatibility

Based on Robert Nyman's page

No support (notably in IE6-8) means that the script will trigger a syntax error.

Feature Firefox (Gecko) Chrome Internet Explorer Opera Safari
Basic support 2.0 (1.8.1) 1 9 9.5 3
Feature Firefox Mobile (Gecko) Android IE Mobile Opera Mobile Safari Mobile
Basic support ? ? ? ? ?

See also


Document Tags and Contributors

Last updated by: Sheppy,