JavaScript Proxy/handler Reference

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

Syntax:

const p = new Proxy(target, {
 Proxy method: function(target, thisArg, argumentsList) {
  }
});

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

<script>
    function sum(a, b) {
      return a + b;
    }
     
    const handler = {
      apply: function(target, thisArg, argumentsList) {
        console.log(`Calculate sum: ${argumentsList}`);
     
        return target(argumentsList[0], argumentsList[1])*14/3;
      }
    };
     
    const proxy1 = new Proxy(sum, handler);
     
    console.log(sum(23, 4));
    console.log(proxy1(23, 4));
</script>

Output:

27
"Calculate sum: 23, 4"
126

The complete list of JavaScript Proxy is listed below:

JavaScript Proxy Constructor: In JavaScript, a constructor gets called when an object is created using the new keyword.

JavaScript Proxy Properties: There are no properties for proxy objects.

JavaScript Proxy Methods: JavaScript methods are actions that can be performed on objects.

• Static Method: If the method is called using the proxy class itself then it is called a static method.

JavaScript Handler Methods: This method is quite different from other javascript methods, this methods handle and verify user input, user actions, and browser actions. It sets the restriction to the browsers same tings does not required to trigger multiple ties as well.