Get DOM elements by class name

getElementsByClassName.js

// recursive method
const getElementsByClassNameRec = (className) => {
  let nodeList = []
  function find(node) {
      if (node.classList && node.classList.contains(className))
        nodeList.push(node)
      for (let i = 0; i < node.childNodes.length; i++)
        find(node.childNodes[i])
      return nodeList
  }
  find(document.body)
  return nodeList
};

// supreme empilhar os elementos e ir substituindo pelos filhos
// array.from coloca todos os filhos do elemento pai em um array
const getElementsByClassName = (className) => {
   let stack = [document.body]
   let nodeList = []
   do {
     let node = stack.pop()
     if (node.classList && node.classList.contains(className))
       nodeList.push(node)
     stack = stack.concat(Array.from(node.childNodes).reverse())
   } while (stack.length > 0)
   return nodeList
}

https://developer.mozilla.org/en-US/docs/Web/API/Document/getElementsByClassName