This article to share js to achieve the click button font zoom in and out of the example code, the code is simple to understand, the need for a friend to refer to it

The specific code is as follows:

<style>
.bb{color:red;}
.cc{color:green;}
.chapter {font-size: 1.5em;}
.normal{font-size:12px;}
.hidden{display:none;}
</style>
<script>
$(document).ready(function() {
$('div.aa').addClass('bb');
$('a[href^="http:"]').addClass('cc');
//$('#switcher-large').on('click',function(){
// $('div.large').addClass('chapter');
//});
$('#switcher-large').click(function(){
$('div.large').toggleClass('chapter');
$(this).toggleClass('bb');
});
//$('#switcher').click(function(){// Click the button to add (remove) styles ( toggleClass Methods)
//$('#switcher button').toggleClass('hidden');
//})
// Zooming in and out of font
var $biger = $('div.large');
var num = parseFloat($biger.css('fontSize'));
$('#switcher-bigger').click(function(){
num=num*1.4;
$biger.css('fontSize',num+'px');
});
$('#switcher-small').click(function(){
num=num/1.4;
$biger.css('fontSize',num+'px');
});
});
</script>
<div id="switcher" class="switcher">
<h3>Style Switcher</h3>
<button id="switcher-default"> Default </button>
<button id="switcher-hidden">Narrow hidden</button>
<button id="switcher-large">Large Print</button>
<button id="switcher-bigger">switcher-bigger</button>
<button id="switcher-small">switcher-small</button>
</div>
<div class="large">
<p> The home of the script </p>
<p> The home of the script </p>
<p> The home of the script </p>
<p> The home of the script </p>
</div>

JavaScript on the realization of click the button font enlargement, reduction of the relevant knowledge to introduce so much, I hope to help you!