14.js

function repeat(operation, num) {
    // Modify this so it doesn't cause a stack overflow!
    if (num <= 0) return;
    setTimeout(function() {
        trampoline(operation);
        repeat(operation, --num);
    }, 0);
    return;
}

function trampoline(fn) {
    // You probably want to implement a trampoline!
    setTimeout(function() {
        fn();
    }, 0);
}

module.exports = function(operation, num) {
    // You probably want to call your trampoline here!
    return repeat(operation, num)
}

// official answer
// function repeat(operation, num) {
//     return function() {
//         if (num <= 0) return
//         operation()
//         return repeat(operation, --num)
//     }
// }
//
// function trampoline(fn) {
//     while(fn && typeof fn === 'function') {
//         fn = fn()
//     }
// }
//
// module.exports = function(operation, num) {
//     trampoline(function() {
//         return repeat(operation, num)
//     })
// }