Here is my code:

/**
 * @NApiVersion 2.0
 * @NScriptType ScheduledScript
 */
define(['N/search'],
    /**
 * @param{search} search
 */
    function(search) {

        const execute = function(scriptContext) {

        }

        return {execute}

    });

SuiteScript 2.0 doesn't support ECMA6 features, so things like "const" don't work. You'd have to set the NAPIVersion to 2.1 for it to work or change "const" to "var"

const does work in 2.0

function functionName() {}

Changing the API version to 2.1 also resolves the error.

const works, what does not work is mixing es6 style declaration with the old style… Therefore if you remove const execute = and you simply do: function execute(scriptContext) {} then it would work.

I had to change it to this to get it to work for 2.0: