Proxy in javascript

The Proxy object enables you to create a proxy for another object, which can intercept and redefine fundamental operations for the object.

get method can redefine the access of an atrribute, it accepts three params(target object, atrribute name and proxy instantiation).

get method can be inherited.

In above code, interception operation is defined on Prototype object, so this interception will be triggered when accessing the inherited attribute ofobj .

set method can intercept an attribute’s assignment operation. It can accepts four arguments (target object, property name, property value, Proxy instantiation).

In above code, any value that does not meet the requirements will trigger an error.

Sometimes, we want to add inner properties with a underscore in an object, which means we don’t want these properties to be used outside. We can take advantage of get and set to achieve this.

In strict mode, set must return turn , or it will cause error.

apply method can intercept invocation, call and apply operation.

apply accepts three arguments (target object, context of the target object(this), argument array of target object).

Example

In above code, p is the instantiation of Proxy. When p is called p() , it will be intercepted by apply method and returns a string.

Another example

Proxy object can intercept any property, so it can be used to implement web server.

Above code creates a web server interface returning different kinds of data. Proxy can intercept any property, so we don’t need to write matching method for every data, just one Proxy is enough.

And Proxy can be used to implement ORM layer for database.

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