JavaScript | Proxy() Object

Last Updated : 14 Feb, 2019

The proxy object in JavaScript is used to define the custom behavior of fundamental operations (e.g. property lookup, assignment, enumeration, function invocation, etc).

Syntax:

var p = new Proxy(target, handler);

Parameter: The proxy object accept two parameters as mentioned above and described below:

target: A target object (can be any sort of object including a function, class, or even another proxy) to wrap with Proxy.
handler: An object whose properties are functions which define the behavior of the proxy when an operation is performed on it.

Example:

                        <script> 
const Person = { 
    Name: 'John Nash', 
    Age: 25 
}; 
  
const handler = { 
    // target represents the Person while prop represents 
        // proxy property. 
    get: function(target, prop) { 
        if (prop === 'FirstName') { 
            return target.Name.split(' ')[0]; 
        } 
        if (prop === 'LastName') { 
            return target.Name.split(' ').pop(); 
        } 
        else { 
            return Reflect.get(target,prop); 
        } 
    } 
}; 
  
const proxy1 = new Proxy(Person, handler); 
  
document.write(proxy1 + "<br>"); 
  
// Though there is no Property as FirstName and LastName,  
// still we get them as if they were property not function. 
document.write(proxy1.FirstName + "<br>"); 
document.write(proxy1.LastName  + "<br>");      
</script>                     

Output:

[object Object]
John
Nash

Note: The above code can be run directly in terminal provided NodeJs is installed, else run it in a HTML file by pasting the above in script tag and check the output in console of any web browser.

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