Getting started with google-visualization – Loading and Running

Google currently has two ways to load the JS library for Google Visualization (a.k.a Google Charts), gstatic loader (https://www.gstatic.com/charts/loader.js) and
jsapi (https://www.google.com/jsapi).

The gstatic loader is recommended because Google is transitioning away from jsapi to the gstatic loader.
See transition reference

In either case, you must first include one of the loaders with a script tag, typically in the head of your document, like this:

<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>

Once you have included the loader in your webpage, you can use it to load the desired library packages by calling a load function.

For Loader.js

google.charts.load('current', {packages: ['corechart']});

For JSAPI

google.load('visualization', '1', {'packages':['corechart']});

But after you load the library packages, you must wait for them to finish being loaded before proceeding to use them. The way to wait is to set up a callback by calling a setOnLoadCallback function.

Sample Code (for the gstatic loader):

<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>
<script>
 google.charts.load('current', {packages: ['corechart']});
 google.charts.setOnLoadCallback(drawChart);
      function drawChart() {

        var data = new google.visualization.DataTable();
        data.addColumn('string', 'Group');
        data.addColumn('number', 'Gender');
        data.addRows([
          ['Males', 10],
          ['Females', 5]
        ]);

        var options = {
            'title':'Gender distribution',
            'width':300,
            'height':300};
        var chart = new google.visualization.PieChart(
            document.getElementById('gender_chart'));
        chart.draw(data, options);
      }
    </script>

HTML:

<div id="gender_chart"></div>

JSFIDDLE

if you want to reproduce, please indicate the source:
Getting started with google-visualization – Loading and Running - CodeDay