Edit in JSFiddle

(function(){

var num1 = get( '#num1' );
var str1 = get( '#str1' );
var num2str = get( '#num2str' );
var str2num = get( '#str2num' );
var run = get( '#run' );
var debugger1 = get( '#debugger1' );

function get( target ) { return document.querySelector( target ); }
function addCommas( number ) { return (+number).toLocaleString(); }
function delCommas( commas ) { return commas.replace(/\,/g, ''); }

function init() {
  run.onclick = function( event ) {
    debugger1.innerHTML = `num1 = ${num1.value} // str1 = ${str1.value}`;
    num2str.innerHTML = addCommas( num1.value );
    str2num.innerHTML = delCommas( str1.value );
  }
} 
init();
})();

<input type="text" id="num1" placeholder="Number"> ==> [<span id="num2str"></span>]
<br/>
<input type="text" id="str1" placeholder="commas"> ==> [<span id="str2num"></span>]
<br/>
<input type="button" id="run" value="RUN">
<br/>
<div id="debugger1"></div>