https://brunch.co.kr/@sunghokimnxag/5

boooooooo.js

function pp(givenNth/*: int*/, curNth = 0/*: int*/, dir = 1 /* { 1 | -1 } */, result = 0/*: int*/) { 
    // console.log(arguments[1], arguments[2], arguments[3]);
    'use strict';
    if (givenNth === curNth) {
        return result;
    } else {
        return pp(givenNth, curNth + 1, isTurnAround(curNth + 1) * dir, result + dir);
    }
}

function isTurnAround(n/*: int*/) {
    'use strict';
    if (n >= 7) {
        if (n % 7 === 0 || n % 10 === 7) {
            return -1;
        } else {
            return isTurnAround(n / 10 | 0);
        }
    } else {
        return 1;
    }
}

// Test for isTurnAround(n)
for (let i = 0; i <= 100; i++) {
    let expected = (i % 7 === 0 || String(i).indexOf('7') > -1) ? -1 : 1;
    let actual = isTurnAround(i);
    console.assert(actual === expected, i);
}

// Test for pp(nth)
console.assert(pp(8) === 6, 8);
console.assert(pp(22) === 0, 22);
console.assert(pp(68) === 2, 68);
console.assert(pp(100) === 2, 100);


// Using proper tail call (TCO) support in Webkit.
// 10000 -> around 20ms
// 100000 -> around 200ms
console.time('pp');
console.log((function () {
    'use strict';
    return pp(10000);
})());
console.timeEnd('pp');