JavaScript handler.ownKeys() Method

The handler.ownKeys() method of JavaScript is used to return an enumerable object. This method is a trap for Reflect.ownKeys().

Syntax

Parameters

target: The target object.

Return value

Return an enumerable object.

Browser Support

Chrome	49
Edge	12
Firefox	18
Opera	36

Example 1

<script>
var proxy1 = new Proxy({}, {
  ownKeys: function(target) {
   document.writeln(" Use handler.ownKeys() is ");
    return ['a', 'b', 'c'];
  }
});
document.writeln(Object.getOwnPropertyNames(proxy1)); 
//expected output: Use handler.ownKeys() is a,b,c
</script>

Test it Now

Output:

Use handler.ownKeys() is a,b,c

Example 2

<script>
var x = {
 Age:24,
 Count: 45
}
var y = {
  ownKeys (target) {
    return Reflect.ownKeys(target)
  }
}
var z = new Proxy(x,y);
for (let key of Object.keys(z)) 
{
  document.writeln(key);
  // expected output: Age Count
 }
</script>

Test it Now

Output:

Age Count

Example 3

<script>
var x = { foo: 1 };
Object.defineProperty(x, 'variable', { value: 2, 
                                  writable: true,
                                enumerable: false,
                                  configurable: true } );

var proxy = new Proxy(x, {
  ownKeys: function(target, a, b) {
    document.writeln('in ownKeys method');
var names = Object.getOwnPropertyNames(target);
    //Useing Object.getOwnProperty mehod.
    var symbols = Object.getOwnPropertySymbols(target);
    return names.concat(symbols);
  }
});
document.writeln(Object.keys(proxy));
//expected.output: in ownKeys method foo 
document.writeln("<br/>")
document.writeln(Object.getOwnPropertyNames(proxy));
//expected output: in ownKeys method foo,variable
</script>

Test it Now

Output:

in ownKeys method foo 
in ownKeys method foo,variable

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