How to use a JS variable in another Custom JS script?

In GTM, it's usually by replacing the var name with {{var name}}. How do I do in this Adobe launch?

I have a custom JS that's simply not reading directly from the console log. However, if I separately declare a Data Element that's a JS variable that reads from performance.timing.requestStart, I can see the value in Cloud Debugger.

How can I apply such variables here for startTime and endTime var in below code?

thanks.

function getPageLoadTime() {

if (typeof(performance) !== 'undefined' && typeof(performance.timing) == 'object') {

var timing = performance.timing;

// fall back to less accurate milestones

var startTime = performance.timing.requestStart;

var endTime = performance.timing.loadEventEnd;

if (startTime && endTime && (startTime < endTime)) {

return (endTime - startTime);

}

}

return 'data not available';

}