JSFiddle - React, Tailwind, and code Playground

HTML

<svg id='foo' >
    <g class='one'></g>
</svg>
<div id='bar'>
    <div class='two'></div>
</div>

JavaScript

var assert = function (condition) { if (!condition) alert("Failed"); }

//Only #foo in array: Success
var containers2 = [$("#foo").get(0)];
assert($(containers2).children().first().is(".one"));
assert($(containers2).children(".one").length === 1);
  
//(Unrelated) #bar in array, too: Fails
var containers = [$("#foo").get(0), $("#bar").get(0)];
assert($(containers).children().first().is(".one")); //Fails
assert($(containers).children(".one").length === 1);