java reflection retrieve method return value

#Java reflection retrieve method return value update
#Java reflection retrieve method return value full

Most of the internal methods are straightforward in what they do. For example, array methods read and write to array through these internal methods, so methods like push() would also invoke get() and set() traps. In each trap's page, we list several typical situations when the trap is invoked, but these internal methods are called in a lot of places.

The Reflect namespace offers methods that do little more than call the internal methods, besides some input normalization/validation.

A delete obj.x may log things to the console, modify some global state, or even define a new property instead of deleting the existing one, although these semantics should be avoided in your own code.Īll internal methods are called by the language itself, and are not directly accessible in JavaScript code. When you run delete obj.x, there's no guarantee that 'x' in obj returns false afterwards - it depends on the object's implementations of ] and ]. This means almost no behavior (except certain critical invariants) is guaranteed in the language - everything is defined by the object itself. It's important to realize that all interactions with an object eventually boils down to the invocation of one of these internal methods, and that they are all customizable through proxies.

#Java reflection retrieve method return value full

Proxy enable developers to define their own exotic objects with full capacity.Īll objects have the following internal methods: Internal methodįunction objects also have the following internal methods: Internal method Such objects whose internal methods have different implementations from ordinary objects are called exotic objects.

#Java reflection retrieve method return value update

This is because arrays have a ] internal method that knows to update length when an integer index is written to, or update the array contents when length is written to. Similarly, adding array elements automatically changes the length property. The obj.x property access syntax simply invokes the ] method on the object, and the object uses its own internal method implementation to determine what to return.Īs another example, arrays differ from normal objects, because they have a magic length property that, when modified, automatically allocates empty slots or removes elements from the array. There isn't anything special about this process in the language - it's just because ordinary objects, by default, have a ] internal method that is defined with this behavior.

If x is an accessor property, the getter is invoked, and the return value of the getter is returned.

If x is a data property, the property descriptor's value attribute is returned.

The x property is searched up the prototype chain until it is found.

For example, when you read obj.x, you may expect the following to happen: However, the language doesn't provide any machinery to directly manipulate data stored in the object - rather, the object defines some internal methods specifying how it can be interacted with.