Proxy : Object

The Proxy allows you to wrap an Object (called the **target**) and

modify the behavior of that Object.

Version:

ECMAScript 2015

Spec:

http://www.ecma-international.org/ecma-262/6.0/#sec-proxy-objects

----

new Proxy(target : Object, handler : ProxyHandler) : Proxy

Creates a new Proxy for the **target** where **handler**

allows you to modify the behavior of **target**.

<example>

// Create a Proxy for Map that only allows even number keys

var evenMap = new Proxy(new Map(), {

// The 'get' function allows you to modify the value returned

// when accessing properties on the proxy

get: function(target, name) {

// Return a custom function for Map.set that checks

// that the keys are even numbers

if (name === 'set') {

return function(key, value) {

if (Number.isInteger(key) && (key % 2 === 0)) {

return target.set(key, value);

}

else {

throw Error('key "' + key + '" is not even');

}

};

}

else {

// Return the normal property value for everything else

return target[name];

}

}

});

evenMap.set(0, 'foo');

console.log(evenMap.get(0));

evenMap.set(2, 'bar');

console.log(evenMap.get(2));

try

{

evenMap.set(3, 'baz');

console.log(evenMap.get(3));

}

catch (e)

{

console.log(e);

}

</example>

Spec:

http://www.ecma-international.org/ecma-262/6.0/#sec-proxy-target-handler

----

revocable(target : Object, handler : Proxyhandler) : Proxy

Spec:

http://www.ecma-international.org/ecma-262/6.0/#sec-proxy.revocable