// JavaScript Document

var min=8;
var max=20;

function increaseFontSize() {
   var body = document.getElementsByTagName('body');  //you may replace "body" for any other tag element if desire to target a specific tag such as <p>
   
   for(i=0;i<body.length;i++) {
      if(body[i].style.fontSize) {
         var s = parseInt(body[i].style.fontSize.replace("px",""));
      } else {
         var s = 12;
      }
      if(s!=max) {
         s += 2;
      }
      body[i].style.fontSize = s+"px"
   }
}

function decreaseFontSize() {
   var body = document.getElementsByTagName('body');
   for(i=0;i<body.length;i++) {
      if(body[i].style.fontSize) {
         var s = parseInt(body[i].style.fontSize.replace("px",""));
      } else {
         var s = 12;
      }
      if(s!=min) {
         s -= 2;
      }
      body[i].style.fontSize = s+"px"
   }
}