js如何获取标签里的子元素

let element = document.getElementById('parentElement');
let children = element.children;
for(let i = 0; i < children.length; i++) {
    console.log(children[i]);
}

let element = document.getElementById('parentElement');
let childNodes = element.childNodes;
for(let i = 0; i < childNodes.length; i++) {
    console.log(childNodes[i]);
}

let element = document.getElementById('parentElement');
let firstChild = element.firstElementChild;
let lastChild = element.lastElementChild;
console.log(firstChild, lastChild);

let element = document.getElementById('parentElement');
let firstChild = element.querySelector(':first-child');
let allChildren = element.querySelectorAll('*');
console.log(firstChild, allChildren);

let element = document.getElementById('parentElement');
let childrenByTagName = element.getElementsByTagName('div');
for(let i = 0; i < childrenByTagName.length; i++) {
    console.log(childrenByTagName[i]);
}