set

Summary

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

Syntax

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

Parameters

prop

the name of the property to bind to the given function

val

an alias for the variable that holds the value attempted to be assigned to prop

Description

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.

A setter can be removed using the delete operator.

Examples

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;

Specifications

Browser compatibility

Based on Robert Nyman's page

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

See also

• delete
• get
• Object.defineProperty()
• __defineGetter__
• __defineSetter__
• Defining Getters and Setters in JavaScript Guide