What is the difference between reflect and proxy?

If you are using a language with dynamic typing, the difference is purely semantic.

If you call a function, it's called on the actual object (the one you are calling it on), and if it has a result it is returned to you. So if you pass an object to a function, it is called on that object and the return value is used.

If you call a function through reflection (from a Java program for example), it's called on the actual class, and the return value is used. So if you pass an object of type T to a function that takes a T, it is called on that object and the return value is used.

In both cases the return value will be the same. It will be the value of the function or method. If the function returns a reference type, the return value will be the reference. If the function returns an array, the return value will be the array.

When to use JS reflect?

Consider the following code.

It is a simple example, but could still be useful to understand how does JS reflect work.
// create a new object (function). Var x = function(). // print the properties of an object (function). Var y = new x(). Console.log(Object. Y references to the updated version of x
Y.x //=> hello console.log(y.x) //=> hello
// and when you say. Console.log(y.x) //=> undefined
// then JS reflect works differently. It only tracks which properties are directly // referenced in the expression. So y.x === "hello" is true, because the x directly
// referred to by y is updated. But y.toString === "function" is false. That is,
// y.toString is not directly referenced. What it indirectly referenced is the y.x
// that is referenced by the constructor (y). To make it a reference to the updated // x, we need to add a property to y first. Let's add it as a side effect.log(y.toString)
//=> "function anonymous()". // now we make a reference to this updated version using y. We get // console.log(y.toString())
//=> "function anonymous()" // y.toString changed as expected // => function (y). // => function (). // => function (). // so what happens when you try to call this object?log(y()()) //=> TypeError: y is not a constructor. From. It seems the use of reflect.

When to use reflect API?

It seems like reflect is a tool mostly to be used in server-side applications for dynamic data or user profiles.

However, I have several questions about when to use it and what benefits do we gain from it? From the documentation: Reflect.defineProperty() can return typeof Undefined as its value to indicate that the property has not yet been added. This is useful if an object contains property identifiers of which some are missing from JavaScript (eg getters). In that case the properties of the object are accessible but the getters themselves must be set.

Are there cases where a getter could appear in JavaScript? Should we be careful when calling reflect.deleteProperty because the property can become non-configurable in JavaScript using Object.defineProperty()) due to a specification change or the property wasn't there from the start (eg an HTML element added later). Can it break our programs if used incorrectly?
Should we use Object.prototype.hasOwnProperty instead?defineProperty() can return typeof Undefined as its value to indicate that the property has not yet been added. This is useful if an object contains property identifiers of which some are missing from JavaScript (eg getters).

The only time this is necessary is with IE9 and earlier where those "getters" don't actually exist. You cannot set a property that doesn't exist.

This is documented in the Notes on Object.defineProperty(): Note: The new Object.defineProperties() method supports defining named properties on an object on Internet Explorer 9 and earlier. When doing so, use the standard Object.defineProperty() method to define properties using the key and descriptor arguments in a similar way to how Object.defineProperties() creates properties.

If your library is going to handle browser incompatibility and the client has old IE software I would say to ignore this behaviour - it's completely incorrect.