A Proxy in JavaScript is a special object that allows you to customize the behavior of fundamental operations (e.g., property lookup, assignment, enumeration, function invocation, etc.) on another object. It's like having a mischievous middleman who can intercept and alter interactions with an object.
Why Do We Need Proxies?
Proxies are useful for various reasons:
Validation: Ensure data integrity by validating assignments.
Logging: Track operations on an object for debugging or monitoring.Default Values: Provide default values when properties are accessed.
Access Control: Restrict or modify access to certain properties.
Virtual Properties: Define properties that don't physically exist on the object.
Funny Examples to Understand Proxies
Example 1: The Overprotective Parent
Imagine you have a kid named Timmy, and you want to make sure he doesn’t eat too many cookies. You act as an overprotective parent, monitoring and controlling his cookie intake.
let timmy = { cookies: 3 }; let overprotectiveParent = new Proxy(timmy, { get(target, property) { console.log(`Overprotective Parent: "Timmy currently has ${target[property]} ${property}."`); return target[property]; }, set(target, property, value) { if (property === 'cookies' && value > 5) { console.log('Overprotective Parent: "No, Timmy, you can’t have more than 5 cookies!"'); return false; } console.log(`Overprotective Parent: "Alright, Timmy, you can have ${value} ${property}."`); target[property] = value; return true; } }); // Checking Timmy's cookies console.log(overprotectiveParent.cookies); // Overprotective Parent: "Timmy currently has 3 cookies." // Trying to give Timmy too many cookies overprotectiveParent.cookies = 6; // Overprotective Parent: "No, Timmy, you can’t have more than 5 cookies!" // Setting a reasonable number of cookies overprotectiveParent.cookies = 4; // Overprotective Parent: "Alright, Timmy, you can have 4 cookies." console.log(overprotectiveParent.cookies); // Overprotective Parent: "Timmy currently has 4 cookies." 
Top comments (1)
Proxies are really usefull. I've created several libraries/modules using them, for example es-string-fiddler or es-date-fiddler.