http://toys.usvsth3m.com/javascript-under-pressure/

arraySum

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 index, entry, ret = 0, len = i.length;
  
    for(index = 0; index < len; index += 1){ 
      entry = i[index];
      ret += entry instanceof Array ? arraySum(entry)) : entry;
    }

    return ret;
}

doubleInteger.js

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

getFileExtension.js

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
    
    var lastIndex = i.lastIndexOf('.');

    return lastIndex > -1 ? i.slice(lastIndex + 1) : false;
    
}

isNumberEven.js

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

    return i % 2 === 0;
}

longestString

function longestString(i) {
    
    // i will be an array.
    // return the longest string in the array
    
    var index, length, current, longestEntry;

    for (index = 0, length = i.length; index < length; index += 1) {
        current = i[index];

        if (typeof current !== 'string') {
            continue;
        } else if (current.length > (longestEntry = longestEntry || current).length) {
            longestEntry = current;
        }
    }

    return longestEntry;
}