test-page.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <!-- <meta http-equiv="refresh" content="5;url=http://www.naver.com/"> -->
    <title>Document</title>
</head>

<body>
    <script>
        let req = new XMLHttpRequest();
        req.open('POST', 'https://openapi.naver.com/v1/datalab/search');
        req.setRequestHeader('Access-Control-Allow-Origin', '*');
        req.setRequestHeader('Content-Type', 'application/json');
        req.setRequestHeader('X-Naver-Client-Id', '9bQxi6RNQGf3G3PEknHS');
        req.setRequestHeader('X-Naver-Client-Secret', 'YOX5qCK8mz');
        // req.setRequestHeader('Content-Length','360');
        var body = {
            "startDate": "2018-12-01",
            "endDate": "2019-01-01",
            "timeUnit": "month",
            "keywordGroups": [
                {
                    "groupName": "한글",
                    "keywords": [
                        "알함브라"
                    ]
                }
            ]

        };
        req.send(body);
        if (req.status == 200) {
            alert(req.responseText);
        }
    </script>
</body>

</html>