JSFiddle - React, Tailwind, and code Playground

HTML

<div id="items">
   <div class="item">
     <div class="item_box" id="id_1">
       <div class="one" id="one"></div>
     </div>
    </div>
   <div class="item">
     <div class="item_box" id="id_2">
       <div class="one" id="two"></div>
     </div>
    </div>
   <div class="item">
     <div class="item_box" id="id_3">
       <div class="one" id="three"></div>
     </div>
    </div>
 </div>

CSS

body {
    padding:15px;
}

div {
    border: 1px solid #000000;
    padding:5px;
    background-color:#EFEFEF;
    margin:5px;
}

JavaScript

$(function(){

    var child = $('#items').find('div.item_box');
                  
    var idArray = new Array();
    
    if(child.length){
        
        $.each(child,function(i,entry){
            
            idArray.push($(this).attr('id'));
            
        });
        
    }
    
    console.log(idArray);

});