How convert items li:
<ul id='list'>
<li>city1</li>
<li>city2</li>
<li>city3</li>
<li>city4</li>
</ul>
‘["city1","city2","city3","city4"]’
>Solution :
const list = document.getElementById("list"),
cities = Array.from(list.children).map(each => each.innerHTML),
citiesJSON = JSON.stringify(cities)
console.log(citiesJSON)<ul id='list'>
<li>city1</li>
<li>city2</li>
<li>city3</li>
<li>city4</li>
</ul>