ES6 Iterate over class methods

This is a bit more elaborated but gets methods from the whole prototype chain.

function getAllMethodNames (obj, depth = Infinity) {
    const methods = new Set()
    while (depth-- && obj) {
        for (const key of Reflect.ownKeys(obj)) {
            methods.add(key)
        }
        obj = Reflect.getPrototypeOf(obj)
    }
    return [...methods]
}

You can use Object.getOwnPropertyNames on the prototype:

Object.getOwnPropertyNames( Animal.prototype )
// [ 'constructor', 'getAnimalType' ]

i know, i know, but hey...

const isGetter = ( x, name ) => ( Object.getOwnPropertyDescriptor( x, name ) || {} ).get
const isFunction = ( x, name ) => typeof x[ name ] === "function";
const deepFunctions = x => 
  x && x !== Object.prototype && 
  Object.getOwnPropertyNames( x )
    .filter( name => isGetter( x, name ) || isFunction( x, name ) )
    .concat( deepFunctions( Object.getPrototypeOf( x ) ) || [] );
const distinctDeepFunctions = x => Array.from( new Set( deepFunctions( x ) ) );
const userFunctions = x => distinctDeepFunctions( x ).filter( name => name !== "constructor" && !~name.indexOf( "__" ) );


// example usage

class YourObject {   
   hello() { return "uk"; }
   goodbye() { return "eu"; }
}

class MyObject extends YourObject {
   hello() { return "ie"; }
   get when() { return "soon"; } 
}

const obj = new MyObject();
console.log( userFunctions( obj ) ); // [ "hello", "when", "goodbye" ]