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JavaScript handler has() Method

JavaScript handler has() Method with examples on javascript handler, javascript methods, javascript tutorial, apply(), construct(), defineProperty(), deleteProperty(), get(), setPrototypeOf(), set(), ownKeys(), isExtensible() etc.

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JavaScript handler.has() Method

The handler.has() method used to "hide" any property you want. It's a trap for an operator. It returns the Boolean value true if you want the property to be accessed, otherwise false If the key is present or not in the original object.

Syntax

has: function(target, prop)

Parameters

target: The target object.

prop: The property to check for existence.

Return value

Return a Boolean value.

Browser Support

Chrome 49
Edge 12
Firefox 18
Opera 36

Example 1

const x = { f:10 };
const proxy = new Proxy(x, {
  has: function(target, name) {
   document.writeln('in has');
     //expected output: in has
 return name in target;
  }
});
document.writeln('f' in proxy);
//expected output: true
Test it Now

Output:

in has true

Example 2

var x={hoo:1}
var xyz = new Proxy(x,  {
  has: function(target, key) {
    if(key == "a") return false;
      return true;
    }
  }
)
var x= ("a" in xyz)	
var y = ("b" in xyz)	
document.write("a in d: " +x)
//expected output: a in d: false
document.write('
');
document.write("b in d: " +y) 
//expected output: b in d: true
Test it Now

Output:

a in d: false
b in d: true

Example 3

var s={
  voo:1
}
var p = new Proxy(s, {
  has: function(target, prop) {
    document.writeln('called: ' + prop);
    return false;
  }
});
document.writeln('a' in p); 
//expected output:called: a false
Test it Now

Output:

called: a false

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