https://www.conicet.gov.ar/wp-content/themes/conicet2018/js/resize.js?ver=6.3.1

1// This prevents the execution of the code before the document is finished loading.
2jQuery(document).ready(function() {
3 
4    // The 'A+' element  in the page is associated with the jQuery click() event.
5    jQuery('#increase-font').click(function(event) {
6 
7        // This prevents the default action of the click() event from being triggered.
8        event.preventDefault();
9        // The jQuery each() event interates over each elements belonging to the 'resize' class
10        jQuery('.resize').each(function() {
11            // Call to a custom function to increase the text size
12            changeTextSize(this, change);
13        });
14    });
15 
16    // The 'A-' element  in the page is associated with the jQuery click() event.
17    jQuery('#decrease-font').click(function(event) {
18 
19        // This prevents the default action of the click() event from being triggered.
20        event.preventDefault();
21        // The jQuery each() event interates over each elements belonging to the 'resize' class
22        jQuery('.resize').each(function() {
23            // Call to a custom function to decrease the text size
24            changeTextSize(this, -change);
25        });
26    });
27});
28 
29// Three variables have been used to define range of the text size and the increment/decrement value respectively.
30var min = 14, max = 24, change = 3;
31 
32// Defines a custom function with two parameters determining the element to be resized and the size
33function changeTextSize(element, value) {
34    var currentSize = parseFloat(jQuery(element).css('font-size'));
35    var newSize = currentSize + value;
36    if (newSize <= max && newSize >= min) {
37    	if (newSize == 23){
38    		jQuery(element).css('font-size', 14 + 'px');
39    	} else if (newSize == 24){
40    		jQuery(element).css('font-size', 15 + 'px');
41    	} else {
42    		jQuery(element).css('font-size', newSize + 'px');
43    	}
44    }
45}