JSFiddle - React, Tailwind, and code Playground
HTML
<input type="text" name="n"/>
<input type="text" name="n"/>
<p id="sum"></p>
<button id="btn"> Get Sum</button>
JavaScript
document.getElementById("btn").addEventListener("click", function() {
var texts = document.getElementsByName("n");
var sum = "";
for( var i = 0; i < texts.length; i ++ ) {
sum = sum + texts[i].value;
}
document.getElementById("sum").innerHTML = sum;
});