demo.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8"/>
    <meta http-equiv="X-UA-Compatible" content="IE=edge"/>
    <meta name="viewport" content="width=device-width, initial-scale=1"/>
    <title>jQuery Chained Selects Demo</title>
    <style type="text/css">
        .container {
            width: 70%;
            margin: 0 auto;
        }

        form {
            margin: 10px;
        }

        select {
            width: 100%;
            font-size: 1.5em;
            padding: 10px;
            margin: 4px 0;
        }

        textarea {
            width: 100%;
            min-height: 500px;
            margin: 10px;
        }
    </style>
</head>
<body>
<div class="container">
    <h2>Form Example</h2>
    <form method="post" action="https://httpbin.org/post">
        <button type="submit">Submit</button>
		<strong id="selected">current</strong>
    </form>
    <h2>Test your JSON Data</h2>
    <textarea id="json">{
	"A": {
		"AA": {
			"1": "AAA"
		},
		"AB": {
			"2": "ABA"
		}
	},
	"B": {
		"BA": {
			"BAA": {
				"3": "BAAA"
			}
		}
	},
	"C": {
		"CA": {
			"4": "CAA"
		},
		"CB": {
			"5": "CBA"
		},
		"CC": {
			"CCA": {
				"6": "CCAA",
				"7": "CCAB"
			}
		}
	}
}</textarea>
    <button id="load_json">Load JSON</button>
</div>

<script src="https://code.jquery.com/jquery-3.5.1.min.js"></script>
<script src="jquery.chained.selects.js"></script>
<script type="text/javascript">
    var chainedData = {};

    function loadJson() {
        $("form select").remove();
        $("<select name=\"example_select\" id=\"example-select\"></select>").insertBefore("form button");
        chainedData = JSON.parse($("#json").val());
        $('#example-select').chainedSelects({
            data: chainedData,
            loggingEnabled: true,
            onSelectedCallback: function (id) {
                if (console !== undefined) {
                    console.log("selected option", id);
                }
                $("#selected").text("selected option: " + id);
            },
        });
    }

    $(document).ready(function () {
        $("#load_json").click(loadJson);
        loadJson();
    });
</script>
</body>
</html>