JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li id="1">Item-1</li>
    <li id="2">Item-2</li>
    <li id="3">Item-3</li>
    <li id="4">Item-4</li>
    <li id="5">Item-5</li>
</ul>

<button type='button'>Get clicked items Id</button>

CSS

li
{
    list-style:none;
    cursor:pointer;
}

JavaScript

var clickedItemsIds = [];
var allLiItems = [];

//this contains all the li items you have defined in your html code
allLiItems = $('li').map(function() { return this; }).get();
console.log(allLiItems);

$('li').click(function(e){
    var itemId = $(e.target).attr("id");
    if(clickedItemsIds.indexOf(itemId) == -1)
    {
        //this contains all the clicked li items
        clickedItemsIds.push(itemId);
    }
});

$('button').click(function(){
    alert("you have " + clickedItemsIds.length + " clicked items in your array, check  the console for values");
    console.log(clickedItemsIds);
});