uncaught in promise referenceerror is not defined javascript code example

Example 1: Uncaught ReferenceError: $ is not defined

<script src="https://code.jquery.com/jquery-1.9.1.js"></script>
<script src="path-para-seu-script"></script>

Example 2: sayHello(); error: Uncaught ReferenceError: sayHello is not defined

sayHello();