Convert Javascript array into human readable list

humanifyArray.js

function humanifyArray(arr, lastWord){
	if (!arr || arr.length === 0){
		// Return an empty string for blank arrays
		return ''
	} else if (arr.length == 1){
		// Return the sole array item if only 1 item
		return arr[0]
	}
	// Duplicate array to prevent modification issues
	arr = arr.slice(0)
	let last = arr.pop()
	// Default lastWord to 'and' if none supplied
	lastWord = lastWord || 'and'
	// Combine and return
	return arr.join(', ') + ' ' + lastWord + ' ' + last
}