JSFiddle - React, Tailwind, and code Playground

HTML

<select id="course">
    <option value="1">Course 1</option>
    <option value="2">Course 2</option>
</select>

<select id="year">
    <option value="1">Year 1</option>
    <option value="2">Year 2</option>
</select>

JavaScript

var courses = {
    1:{years:2},
    2:{ years:3},
    };

$("#course").change(function(){
    var course = $(this).val();
    var options = [];
    for(var i = 1; i <= courses[course].years; i++)
    {
        options.push($("<option/>").attr("value",i).html("Year "+i));
    }
    
	$("#year").html(options);
});