[javascript] How can I count the number of elements with same class?

You can get to the parent node and then query all the nodes with the class that is being searched. then we get the size

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var parent = document.getElementById("parentId");_x000D_
var nodesSameClass = parent.getElementsByClassName("test");_x000D_
console.log(nodesSameClass.length);
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<div id="parentId">_x000D_
  <p class="prueba">hello word1</p>_x000D_
  <p class="test">hello word2</p>_x000D_
  <p class="test">hello word3</p>_x000D_
  <p class="test">hello word4</p>_x000D_
</div>
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