JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <td>T1</td>
        <td>T2</td>
        <td>T3</td>
    </tr>
    <tr>
        <td>t4</td>
        <td>t5</td>
        <td>t6</td>
    </tr>
</table>
<input type="button" value="Togle" onclick="togalFontSize();">

JavaScript

var min=10;
var max=18;
function togalFontSize() {

   var p = document.getElementsByTagName('td');
   for(i=0;i<p.length;i++) {

      if(p[i].style.fontSize) {
         var s = parseInt(p[i].style.fontSize.replace("px",""));
         if(s==max) {
              s = min;
          }else{
             s =  max;
          }
      } else {

         var s = 10;
      }

      p[i].style.fontSize = s+"px"

   }
}