How does js (without jquery) determine how many times a div tag appears on the page?

1. Get the element with the specified id: document.getElementById("specified id value");

2. Get the element based on the specified name attribute: document.getElementsByName("set The value of the specified name attribute");

3. Get all elements of the specified tag name: document.getElementsByTagName("Specified tag name");

4. Custom method , find all elements with the same value based on the value of the given class attribute: /**

*? Query all tags containing the specified class value.

*?@param?className?Specified class name, type: String.

*?@param?parent?Parent node, if not filled in, the search will start from the body tag by default, type: HTTPDocument.

*?return?Returns all found elements, type: Array

function?getElementsByClassName(className,?parent){

parent?=?(parent?==?undefineddocument.body?:?parent);

var?childrenList?=?parent.children;

var?i ?=?0,?len?=?childrenList.length;

var?list?=?[];

while(?i?

var?list?=?[];

while(?i? p>

var?nowNode?=?childrenList[i];

var?classNames?=?nowNode.className.split("?");

var?j ?=?0,?lenj?=?classNames.length;

while(?j?

if(nowNode.className?===?classNames [j]){

list.push(nowNode);

break;

}

j++;

< p>}

var?cList?=?[];

if(?nowNode.children.length?>?0?){

cList? =?getElementsByClassName(className,?nowNode);

}

list?=?list.concat(cList);

i++;

< p>}

return?list;

}