JSFiddle - React, Tailwind, and code Playground

HTML

<div class="singlefunc">singlefunc</div>
<div class="singlefunc">singlefunc</div>
<div class="singlefunc">singlefunc</div>
<div class="singlefunc">singlefunc</div>
<br>
<div class="multifunc">multifunc</div>
<div class="multifunc">multifunc</div>
<div class="multifunc">multifunc</div>
<div class="multifunc">multifunc</div>

JavaScript

var multifunc = function (nodes) {
    var i;
    for (i = 0; i < nodes.length; i += 1) {
        nodes[i].onclick = function (e) {
            var index = i;  
            alert(i);
        };
    }
};

multifunc(document.querySelectorAll('.multifunc'));


var singlefunc = function (nodes) {
    var i;
    for (i = 0; i < nodes.length; i += 1) {
        nodes[i].onclick = function (i) {
            return function (e) {
                alert(i);
            };
        }(i);
    }
};

singlefunc(document.querySelectorAll('.singlefunc'));