JAVASCRIPT

javascript get all elements with class

const allElementContainGrepperClassName = document.querySelectorAll('.grepper');
// => return array of all elements 

const firstElementContainGrepperClassName = document.querySelector('.grepper');

javascript get all methods of class

class Foo {
  public doSomething(){
    return 5;
  }
}

let foo = new Foo();
let propertyNames = Object.getOwnPropertyNames(Object.getPrototypeOf(foo));

javascript get all elements by class starting with

document.querySelectorAll("[class^=page]")