Related Articles

Related Articles

JavaScript | handler.setPrototypeOf() Method
  • Last Updated : 27 Mar, 2020

The handler.setPrototypeOf() method in JavaScript is a trap for Object.setPrototypeOf() method and it returns a Boolean value.

Syntax:

const p = new Proxy(target, {
  setPrototypeOf: function(target, prototype) {
  }
});

Parameters: This method accept two parameters as mentioned above and described below:

  • target: This parameter is the target object.
  • prototype: This parameter is the object’s new prototype or null.

Return value: This method returns a boolean value. It returns true if the [[Prototype]] was successfully changed.

Below examples illustrate the handler.setPrototypeOf() method in JavaScript:



Example 1:

filter_none

edit
close

play_arrow

link
brightness_4
code

<script>
const handler1 = {
  setPrototypeOf(gfg, gfgProto) {
    gfg.geneticallyModified = true;
    return false;
  }
};
  
const gfgProto = {};
const gfg = {
  geneticallyModified : false
};
  
const proxy1 = new Proxy(gfg, handler1);
console.log(Reflect.setPrototypeOf(proxy1, gfgProto));
console.log(gfg.geneticallyModified);
  
var soo={  
  foo:1  
}  
var proxy = new Proxy(soo, {  
  setPrototypeOf(target, newProto) {  
  }  
});  
console.log('a' in proxy); 
</script>

chevron_right


Output:

false
true
false

Example 2:

filter_none

edit
close

play_arrow

link
brightness_4
code

<script>
const handlerThrows = {
    setPrototypeOf(target, newProto) {
        throw new Error('custom error');
    }
}; 
  
const newProto = {}, target = {};
  
const p2 = new Proxy(target, handlerThrows);
document.writeln(Object.setPrototypeOf(p2, newProto));  
document.writeln(Reflect.setPrototypeOf(p2, newProto));
</script>

chevron_right


Output:

Error: custom error

Supported Browsers: The browsers supported by handler.setPrototypeOf() method are listed below:

  • Google Chrome
  • Firefox
  • Opera
  • Safari
  • Edge

full-stack-img




My Personal Notes arrow_drop_up
Recommended Articles
Page :