JavaScript handler.apply() Method

The handler.apply() method is used to trap for a function call. The value returned by the apply trap is also going to be used as the result of a function call through a proxy.

Syntax

Parameters

target: The target object.

thisArg: thisArg use for the call.

argumentsList: The list of arguments used for the call.

Return value

This method can return any value.

Browser Support

Chrome	49
Edge	12
Firefox	18
Opera	36

Example 1

 var o = function(arg1, arg2) {
  document.writeln('proxy value(' + arg1 + ', ' + arg2 + ')');
};
var proxy = new Proxy(o, {
  apply: function(target, thisArg, parameters) {
    document.writeln('First exam..');
    
document.writeln("</br>");
    return target.apply(thisArg, parameters);
  }
});

proxy('23', '54');

Test it Now

Output:

First exam.. 
proxy value(23, 54)

Example 2

var str = function(arg1, arg2) {
  document.writeln('in x(' + arg1 + ', ' + arg2 + ')');
};
var proxy = new Proxy(str, {
  apply: function(target, thisArg, parameters) {
   document.writeln('in apply');
        document.writeln("<br/>");

    return target.apply(thisArg, parameters);
  }
});
proxy('direct1', 'direct2');

proxy.apply(null, ['add', 'add']);
proxy.call(null, 'string', 'string');

Test it Now

Output:

in apply 
in x(direct1, direct2) in apply 
in x(add, add) in apply 
in x(string, string)

Example 3

function p (a) 
{
  return a ;
}
var q = {
  apply: function(target, thisArg, argumentsList) {
   return target(argumentsList[0], argumentsList[1])*2;
  }};
var pro = new Proxy(p, q);
 document.writeln(p(56)); 
document.writeln("<br/>"); 
    document.writeln(pro(34));

Test it Now

Output: