JS function: stringify table (2D array)

stringify-table.js

function stringifyTable(arr) {
	var longest = 0;
	return arr.map(function(innerArr) {
		innerArr = trimArray(innerArr).map(val => '' + val);
		longest = Math.max(longest, Math.max(innerArr.map(val => val.length)));
		return innerArr;
	}).map(function(innerArr) {
		return innerArr.map(function(val) {
			return padLeft('' + val, longest, ' ');
		}).join();
	}).join(',\n');
}

// trim undefined values from ends of array
function trimArray(arr) {
	for (var start = 0; start < arr.length && !(start in arr); start++);
	for (var end = arr.length; end > start && !(end - 1 in arr); end--);
	return arr.slice(start, end);
}

// pad string with extra characters on left to ensure at least len characters
function padLeft(str, len, char) {
	return str.length >= len ? str : new Array(len - str.length + 1).join(char) + str;
}