How can JavaScript\'s Proxy Object be used to implement dynamic getters and setters?

Implementing Dynamic Getters/Setters in JavaScript

Understanding how to create getters and setters for predefined properties in JavaScript is a common concept. However, extending this functionality to encompass dynamic handling of any property name that is not explicitly defined poses a unique challenge.

Dynamic Getter and Setter Functionality in PHP

PHP utilizes the __get() and __set() magic methods to dynamically define getter and setter behaviors for any property. This provides a convenient and flexible approach to manipulate properties on the fly.

JavaScript's Proxy to the Rescue

As of ES2015, JavaScript introduced proxies, a game-changer for dynamic getter and setter implementation. Proxies allow the creation of objects that serve as facades for other objects, enabling the interception and modification of property access.

Example of Using Proxies for Dynamic Getters/Setters

Let's consider the following example, where all non-existent property values will return "missing" and string property values will be transformed to uppercase upon retrieval:

<code class="javascript">"use strict";
if (typeof Proxy == "undefined") {
    throw new Error("This browser doesn't support Proxy");
}
let original = {
    example: "value",
};
let proxy = new Proxy(original, {
    get(target, name, receiver) {
        if (Reflect.has(target, name)) {
            let rv = Reflect.get(target, name, receiver);
            if (typeof rv === "string") {
                rv = rv.toUpperCase();
            }
            return rv;
        }
        return "missing";
      }
});</code>

Testing the Dynamic Behavior

console.log(original.example = ${original.example}); // "original.example = value"
console.log(proxy.example = ${proxy.example}); // "proxy.example = VALUE"
console.log(proxy.unknown = ${proxy.unknown}); // "proxy.unknown = missing"
original.example = "updated";
console.log(original.example = ${original.example}); // "original.example = updated"
console.log(proxy.example = ${proxy.example}); // "proxy.example = UPDATED"

As demonstrated, the proxy intercepts property accesses and applies the defined behavior for non-existent properties ("missing") and string properties (uppercase conversion). It also allows modifications to the original object, with the proxy reflecting the changes made.

Browser Compatibility

Proxies are supported in all major modern browsers, including Chrome, Firefox, Edge, Safari, and Internet Explorer 11 .

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