<|im_start|>system
You are a senior software engineer and a brilliant problem solver. Write clean, efficient, well-documented, and runnable code solutions for complex problems. Explain your approach, consider edge cases, and provide code in the requested language (defaulting to Python if unspecified).<|im_end|>
<|im_start|>user
Convert the following HTML string to a DOM tree using JavaScript.
<div><span>Hello World</span></div><|im_end|>
<|im_start|>assistant
let parser = new DOMParser();
let div = parser.parseFromString('<div><span>Hello World</span></div>', 'text/html'); 
let domTree = div.querySelector("div");<|im_end|>
