JavaScript Does JavaScript in the browser have a reflection mechanism? does javascript run in browser or server,does javascript run

I would like to get a list of all the properties, styles, events and methods of an HTML element. Is there a reflection API in the browsers?

I'm looking for something like this:

var button = new HTMLButtonElement();
var className = document.getQualifiedClassName(button); // "HTMLButtonElement"
var definition = document.getDefinition(className); // HTMLButtonElement reference
var instance = document.getInstance(definition); // instance of HTMLButtonElement
var properties = document.getProperties(button); // properties of HTMLButtonElement
var methods = document.getMethods(button); // methods of HTMLButtonElement
var styles = document.getStyles(button); // styles applicable to HTMLButtonElement
var events = document.getEvents(button); // events on HTMLButtonElement
var inheritance = document.getInheritance(button); // HTMLButtonElement > HTMLElement

EDIT:
This is the call in ActionScript3 that gets what I'm looking for:

var objectInformation = document.describeType(button) // metadata

This may make it more clear what I'm trying to do in JavaScript.

Background
Let's say I'm trying to add code complete to a HTML code editor. When the user puts their cursor next to a div element and initiates code complete, I want to show them all the events and attributes and styles in the code complete pop up. When they are typing in JavaScript, I want to auto complete all the methods that are available. When they start to type in the styles object I want to provide a list of styles.

If I'm given an object or a tag name I need to be able to show all the metadata for code completion. In many languages there are API's to do this.

Answer:1

There's nothing like AS3's describeType in JS. You're asking for a lot of things at once, some of which you can get in JS and some of which you can't (and some of which may not even make sense in JS because it's so dynamic.)

You can certainly get the properties and methods of an object and its hierarchy using Object.getOwnPropertyDescriptors() and Object.getPrototypeOf().

function describeType(object) {
    const prototype = Object.getPrototypeOf(object);
    console.log("Hello, I am a", prototype.constructor.name);
    console.log("My properties are", Object.getOwnPropertyDescriptors(object));
    console.log("My prototype proterties are", Object.getOwnPropertyDescriptors(prototype));
    const superPrototype = Object.getPrototypeOf(prototype);
    if (superPrototype) {
        console.log("My super class is", superPrototype.constructor.name);
        // etc
    }
}

Example on jsfiddle.

Answer:2

You have to define what each of things means.

var className = document.getQualifiedClassName(button);

What does this mean? You can use classList.

var definition = document.getDefinition(className);

What does this mean? Do you mean CSS rules? You will have to walk the CSS object model to find this.

var instance = document.getInstance(definition);

What does this mean? You may be able to use querySelectorAll.

var properties = document.getProperties(button);

If you really mean properties, you can simply traverse the properties of the button as object.

var methods = document.getMethods(button);

Most of the interesting methods will be on prototypes such as HTMLElement, and you have to look for them there. Many or most will be non-enumerable, and may be hard to track down.

var styles = document.getStyles(button);

What do you mean? button.style?

var events = document.getEvents(button);

There is no way to get these.

var inheritance = document.getInheritance(button);

What does this mean?

You can also get attributes, which are distinct from properties:

var attributes = button.attributes;

Answer:3
var button = document.createElement('button')

for(key in button){
 //do anything here
}

You can do this I think.

Answer:4

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