My answers for the http://toys.usvsth3m.com/javascript-under-pressure/ challenge. Please question/comment/improve!!

js-under-pressure.js

// 1
function doubleInteger(i) {
  // i will be an integer. Double it and return it.
	
	return i*2;
}

// 2
function isNumberEven(i) {
	// i will be an integer. Return true if it's even, and false if it isn't.
	
	return !(i%2)
}

// 3
function getFileExtension(i) {
	// i will be a string, but it may not have a file extension.
	// return the file extension (with no period) if it has one, otherwise false
	
	return (i.match(/\.(.+)$/)||[,false])[1];
	// for an explanation of this very useful snippet,
	// see http://james.padolsey.com/javascript/match-trick/
}

// 4
function longestString(i) {
	// i will be an array.
	// return the longest string in the array
	
	return i.sort(function(a,b){
		if (typeof a != 'string') return;
		
		return a.length > b.length;
	}).pop();
}

// 5
function arraySum(i) {
	// i will be an array, containing integers, strings and/or arrays like itself.
	// Sum all the integers you find, anywhere in the nest of arrays.
	
	var sum = 0;

	i.forEach(function(j) {
		if (typeof j == 'number') {
			sum += j;
		} else if (Array.isArray(j)) {
			sum += arraySum(j);
		}
	});

	return sum;    
}