Find the sum of all the multiples of 3 or 5 below 1000.

project-euler-problem-1.2.js

// Do the maths
for(
    var sum = 0, i = 1;
    i < 1000;
    !(i % 3 && i % 5) && (sum += i), i++
);
// Log the result
console.log(sum);

project-euler-problem-1.js

// Prep the array
for(
    var arr = [], i = 1;
    i < 1000;
    !(i % 3 && i % 5) && arr.push(i), i++
);
// Sum the array
console.log(
    arr.reduce(
        function(prev, current) {
            return prev + current
        }
    )
);

project-euler-problem-1.py

print sum([i for i in range(1000) if not (i % 3 and i % 5)])

project-euler-problem-1.rb

puts (1...1000).select{ |n| n % 3 == 0 || n % 5 == 0 }.reduce(:+)

Super useful. thanks for posting this with the different code options.