获取任何对象的所有方法？

Question

In python word there are dir() function which

return a list of valid attributes for that object

In JS words I found:

Object.getOwnPropertyNames

Object.keys

but they don't show ALL attributes:

> Object.getOwnPropertyNames([])
[ 'length' ]

How to get list of all attributes and methods as

concat, entries, every, find.... 

for Array() for example?

Answer 1

You can use Object.getOwnPropertyNames with Object.getPrototypeOf in order to traverse the prototype chain and collect all own properties on each object.

 var result = [] var obj = [] do { result.push(...Object.getOwnPropertyNames(obj)) } while ((obj = Object.getPrototypeOf(obj))) document.querySelector("pre").textContent = result.join("\\n")

 <pre></pre>

This handles all properties irrespective of whether or not they're inherited or enumerable. This does not include Symbol properties however. To include those, you can use Object.getOwnPropertySymbols .

var result = []
var obj = []
do {
  result.push(...Object.getOwnPropertyNames(obj), ...Object.getOwnPropertySymbols(obj))
} while ((obj = Object.getPrototypeOf(obj)))

Answer 2

Object.getOwnPropertyNames(Array.prototype)

The reason why trying to get the values the way you posted does not work, is because you are requesting the property names for a single instance of the Array object. For a number of reasons, each instance will only have property values that are unique to that instance. Since the values found in Array.prototype are not unique to a specific instance -- which makes sense, not all arrays are going to share the same value for length -- they are shared/inherited for all instances of Array .

Answer 3

You could use Object.getOwnPropertyNames

The Object.getOwnPropertyNames() method returns an array of all properties (enumerable or not) found directly upon a given object.

 console.log(Object.getOwnPropertyNames(Array.prototype));

 .as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 4

This method will allow you to pull all the keys and functions from a particular instance of an object (ignoring the unwanted ones):

const ROOT_PROTOTYPE = Object.getPrototypeOf({});

function getAllKeys(object) {
    // do not add the keys of the root prototype object
    if (object === ROOT_PROTOTYPE) {
        return [];
    }

    const names = Object.getOwnPropertyNames(object);

    // remove the default constructor for each prototype
    if (names[0] === 'constructor') {
        names.shift();
    }

    // iterate through all the prototypes of this object, until it gets to the root object.
    return names.concat(getAllKeys(Object.getPrototypeOf(object)));
}